Car AC Not Blowing Cold Air – Charging Tips and FAQ’s

8:45 am Air Conditioning, DIY, How To Auto Repair
DIY’s can possibly prolong the life of their AC with some guidance
©  Summary: One of our most common questions about air conditioning has to do with “how to charge a car’s ac.” In this auto repair blog, we cover the do’s and dont’s of DIY car AC refrigerant charging. We have suggestions on how to fill a car’s air conditioning system if doing it yourself. We caution DIY’s of the dangers and the possibility of over-charging a car’s air conditioner. Questions and answers covering AC gauge sets, charging kits, troubleshooting, refrigerant, leaks and much more. Basic step by step directions are provided.
Low refrigerant is the most common cause of a car’s air conditioner not cooling well. There are many other reasons a car’s A/C may be blowing out warm air though. We strongly recommend the use of an AC manifold gauge set when checking a system. Realistically, we understand that many people are only looking for a quick fix and will purchase a do it yourself-er charging hose or a charging kit to add Freon. The purpose of this article is to help those that are going to use a recharge kit to add refrigerant and take their chances. Keep in mind that if a car has a very slow leak, just adding a can every summer may be feasible; but if there’s a fast leak, adding freon is like throwing money out the window. Be sure to click on our related “how to” car repair articles at the bottom of this page for information on using an AC manifold gauge set and detecting refrigerant leaks.
Step by step directions for simply adding freon to an R134 A system.
1. Locate the low side service port. Do not connect to charge hose at this time. The quick connect fittings are different sizes on the low and high sides, this makes hooking into the high side impossible with a do it-yourself charging kit. The service port cap will be black or sometimes blue. It is in the larger diameter line (suction side) or depending on the system, the accumulator.
2. Read warnings and handling information on the refrigerant can. Safety glasses are recommended to protect your eyes. Avoid skin contact with refrigerant. Make sure the piercing needle is retracted and then connect the screw fitting to the top of the can.
3. Start the engine in the car and turn on air conditioning. Set controls to maximum cooling. Connect the charging kit to the low side service port located in step one. The quick connect spring coupler will need to be pulled back while the fitting is pushed onto the port. After it is in place push the sleeve to go back into the down position. Make sure it is in the locked position and is fully engaged.
4. Turn the valve’s knob to the right which will pierce the can. Turn the knob back to the left which will allow the flow of refrigerant (134A) into the car’s AC system. The can should be held upright and shaken. The reason for not holding the can upside down is that vapor will rise to the top of the can. Liquid will be in the bottom. If liquid is allowed to go in to the car’s A-C system and enters the compressor, as a liquid, the A/C compressor may be damaged. The compressor CANNOT compress liquid. Rotating the can quickly between the 12:00 position and 3:00 position while shaking, will help to vaporize the refrigerant while charging.
5. You may feel the can getting cold while charging – this is normal. Get a feel for the refrigerant in the can so it can be determined if there is any remaining in the can while charging. Once it feels empty, the can will be turned upside down to insure the last bit has been drawn into the car’s AC system.
6. If the car is blowing cold air now, the job is almost complete. Avoid adding too much, I’ve said it before in my other articles “more isn’t always better.”  (That’s why it’s better to use an AC manifold gauge set when charging.) Close the valve by turning it to the right. Disconnect the quick connect fitting and replace the cap onto the service port.
Questions and Answers – FAQ’s
Question – How do I know if my car has 134A?
Answer – Cars manufactured from 1996 and up will most likely have 134A. The 134A type quick connect fittings are a good indicator. Older cars that have not been retrofitted (that still have R12) will have smaller fittings which are threaded, NOT quick connect type fittings.
Question – How do I know how much freon to add to top off my system?
Answer – You don’t. The only way to know 100% is to use an AC recovery machine to remove all the refrigerant. Vacuum the system down using a vacuum pump and then use a weight scale to put the factory specified amount back in. Mechanics with experience can use gauge sets to help them make an educated guess on how much to add. Our article linked at the bottom covers more when it comes to gauge readings and what they mean.
Question – How do I jump my low pressure switch to make my compressor come on so I can charge the system?
Answer – There’s no need to jump the low pressure switch. The compressor will come on when enough pressure is in the system for it to run without it being damaged.
Question – I’ve just replaced my compressor. How do I vacuum the system down first before I charge the system?
Answer – If evacuating and recharging the system, you need an AC manifold gauge set and a vacuum pump, below are basic steps.
  •  Measure oil removed when the system has been emptied. The only legal way to empty a system is with an AC recovery unit.
  • Replace the refrigerant oil that was previously measured. Note that some replacement compressors come with oil in them others do not. Lack of oil may ultimately cause compressor failure, just like running a car motor without engine oil will cause seizing. (old oil is not to be reused). Turn the replacement compressor’s shaft 10-15 times by hand to displace refrigerant oil (this will help prevent damage to the compressor).
  • Vacuum the system down with an AC vacuum pump. The AC manifold gauges should both be OPEN while doing this. The longer the better, but 15-20 minutes ok.
  • 28-29 inches of vacuum should remain, if there’s no major leaks. Close both valves, remove vacuum pump. Connect to refrigerant source. Start engine and turn AC on. Start charging the system by opening the BLUE valve which is the low side. Warning: opening the red valve (attempting to charge through the high side) can possibly cause the refrigerant can to rupture!
  • Use cans so you know how much refrigerant you are putting in or a scale that weighs the bulk container.
Question – I charged my system but it didn’t stay cold for very long. What could be the problem?
Answer – Most likely there’s a leak that is too fast to make occasionally charging feasible. Use a refrigerant leak detector to determine where the leak is and replace the leaking component. See our article linked below about how to find refrigerant leaks.
Question – Since you sell them, parts stores and even Walmart sells charging kits; why don’t you recommend them?
Answer – Using a simple charging kit with NO gauge is like walking in the dark. You may find your way around, but you may stub your toe! Adding freon to a system without a gauge set makes it much more difficult to end up with a proper amount of charge since there’s blind guesswork involved.
Question – I know I have a coolant leak in my AC system. Should I use the freon kit that has stop leak in it?
Answer – Not a good idea. The stop leak may slow the leak down. It may also damage the compressor, clog up the condenser, evaporator or expansion valve. If you end up taking the car to a repair shop and they find that there’s stop leak in the system – they most likely will refuse to work on it. Stop leak wreaks havoc to expensive recovery units. In fact we sell a filter to help prevent damage to AC recovery machines because it is such a problem. Just to clarify; the refrigerant in the AC system is NOT called “coolant.” Coolant or anti-freeze is in the radiator/car engine’s cooling system NOT the air conditioning system.
Question – I need change a part in my AC, how do I get the freon out?
Answer – Take it to a shop and have them recover the refrigerant. Then take the car home and change the failed part. It’s the only way to remove the refrigerant without having an expensive RRR (Recovery, Recycle & Recharge) machine. A recent customer mistakenly thought that a vacuum pump was designed for recovering/emptying a system – this is NOT the case.
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329 Responses
  1. Eric Anderson :

    Date: July 26, 2010 @ 1:40 pm

    My car will run cold A/C for about 5 to 10 minutes and then it will go out. but after about a half hour of not driving it will come back on and do the same thing.

  2. dennisb - Auto Tool Sales :

    Date: August 7, 2010 @ 7:59 pm

    Eric, it could be icing up. See our other AC articles or ask a tech for more personalized help on our car questions page.

  3. joanna mcbride :

    Date: August 13, 2010 @ 7:05 pm

    I just put a new ac compressor on my 2000 Ford windstar and my van is still not getting cold. What else could be my problem?

  4. dennisb - Auto Tool Sales :

    Date: August 14, 2010 @ 8:08 am

    Joanna, You don’t include the reason for compressor replacement to begin with, condition of orifice tube, if you flushed the system, gauge readings and any other components replaced etc. So, I would recommend reading our article called” Adding Freon to Car AC – Gauge Readings Explained.” This may help to determine what the problem is. If you are still having a problem, you may want to visit our car questions page to get more personalized help. Good Luck.

  5. david :

    Date: August 18, 2010 @ 11:30 pm

    My a/c isnt blowing cold air. I went and got some refrigerant with a gauge and figured it was just low and needed a boost but when I put the gauge on it shot all the way to the right. If it was over charged would that cause it to not be cold?

  6. dennisb - Auto Tool Sales :

    Date: August 19, 2010 @ 6:11 am

    Sure. AC condenser fan or radiator fan could also cause the pressures to read high. See our related article on AC Gauge Readings Explained for more information.

  7. James :

    Date: August 21, 2010 @ 1:13 am

    02 Galant AC went out about 3 years ago.. shop added freon worked about 2 months then would cool a few minutes before blowing warm air. Hadn’t even tried till recently…compressor doesn’t seem to cut on… windshield seems to have slight fog like the heater core is going bad. What tools beyond the gauges and pump(I hope a shop will recover the old freon) will I need on a complete system repair. My work comute is 2 hours and my kids are melting. Thanks for any insight.

  8. dennisb - Auto Tool Sales :

    Date: August 21, 2010 @ 6:27 am

    James, the first step is to diagnose the problem. Most techs will add refrigerant if needed, to check for leaks and proper operation of the compressor. Once you know which parts leak or have failed, you can decide if it’s a job you are equipped to handle. As far as the fog on the iside of the windshield; this most likely is moisture from the air. When the AC is working, it pulls a lot of moisture out of the passenger compartment reducing moisture build-up on the inside of the windows (inside window fog). If the heater core is leaking, anti-freeze would have to be added and you may smell a sweet kind of sickening odor inside the car. The heater core leaking would also cause the inside window fog to be very filmy to the touch. An AC manifold gauge set and a leak detector would be the first tools needed. An AC vacuum pump would be used after any repair has been done.

  9. James :

    Date: August 21, 2010 @ 11:36 am

    Thanks Dennis. The system is properly charged( per Express Oil). I thought you might recomend a good basic gauge set and A/C Line Disconnect Tool before I get started troubleshooting.

    Thanks, James

  10. dennisb - Auto Tool Sales :

    Date: August 22, 2010 @ 1:05 pm

    James, Any of the gauge sets for 134A will work fine – just make sure it is for 134A and not just R12. Click on the image at the bottom of the article to visit our ac tool section. Thanks for visiting.

  11. Wil A :

    Date: September 10, 2010 @ 1:18 am

    Hi – I had a mechanic install a new radiator for my ’93 Town&Country minivan and now no more leaks and overheating. Now the A/C isn’t blowing cold air anymore – it was working fine before the radiator replacement. Could he have accidentally disconnected the A/C line and drained freon? I hope he doesn’t think I’m going to easily pay for an A/C fix. Thanks in advance.

  12. dennisb - Auto Tool Sales :

    Date: September 10, 2010 @ 6:23 am

    Wil, it’s possible that an ac refrigerant line or the condenser could have started leaking. It could also be as simple as a bad electrical connection to the AC compressor’s clutch coil (an unplugged coil). I would take it back and ask them to recheck it (without accusing). Let’s remember the vehicle is 17 years old and things do fail… it could just be a coincidence – stranger things have happend.

  13. cyred :

    Date: October 27, 2010 @ 11:24 am

    My car ac compressor is working without leaks however it is not blowing cold air. If I’m running continuously it will blow cold air for a while and when i’m at idle it blows hot air.

    Could you tell me what steps i need to take to fix this thing?


  14. dennisb - Auto Tool Sales :

    Date: October 27, 2010 @ 11:41 am

    Sounds like it is not pumping sufficiently. At idle the AC compressor is turning the slowest – lower RPM’s. If it is starting to fail, lack of performance at idle is what you would expect. High and low presssure readings will tell the story.

  15. cyred :

    Date: October 27, 2010 @ 11:50 am

    thanks for the reply… i shall get back hopefully by tomorrow for the readings.

  16. dennisb - Auto Tool Sales :

    Date: October 27, 2010 @ 12:33 pm

    See our “AC gauge readings explained” car repair article for more information. It’s linked above in related repair articles section.

  17. mike :

    Date: January 30, 2011 @ 5:19 pm

    Where is the a/c port on a ford 98 truck? It’s a 4.6 V-8. I can find the high side service port, but not the low side.

  18. dennisb - Auto Tool Sales :

    Date: January 30, 2011 @ 7:03 pm

    Mike, on most vehicles the the low side service port is located on the side of the acumulator. That is the “can shaped part” on the passenger side near the firewall. See the black cap on the one in the image below.
    Ford F150 Accumulator

    Other times the low side service port may be located on the low side suction line. That is the largest AC line under the hood.

  19. Billy Glidewell :

    Date: May 11, 2011 @ 10:36 pm

    How long after adding freon to vehicle to make sure it holds and not leaking.

  20. dennisb - Auto Tool Sales :

    Date: May 12, 2011 @ 6:22 am

    Billy, it obviously depends upon the severity of the leak, how much the system holds to begin with… or if the system even has a leak at all. Good Luck.

  21. Tim Wang :

    Date: May 30, 2011 @ 11:33 am

    I have a Sienna 01. I add 2 cans 134a each year started two years ago. Yesterday I added 2 cans 134a again. Surprisingly there was no cold air. I measured the low end the pressure was 65 PSI. Any suggestions? Thanks.

  22. Chris :

    Date: June 11, 2011 @ 2:23 pm

    I just replaced the a/c compressor, drier, and orifice tube due to that my A/C compressor was leaking. A/C compressor was reman. and other parts were new. I had the system vacuumed and charged yet my air is still not cold. It blows cooler than what it does if you cut the air off but yet not cold just kinda cool (luke warm). Possible explanation? the shop said it could be a bad orifice tube or compressor. compressor clutch does cycle on along with fans.

  23. dennisb - Auto Tool Sales :

    Date: June 11, 2011 @ 2:53 pm

    Shop should look at readings to help diagnose.

  24. Reynae :

    Date: June 23, 2011 @ 1:47 pm

    HELP! I have a BMW and the A/C is not cooling. I have added freon twice and it is not holding. Does this mean I have a leak?

  25. dennisb - Auto Tool Sales :

    Date: June 23, 2011 @ 2:11 pm

    Adding and then Freon being lost is a very good sign of a leak. I would check with an AC Leak Detector, like the one below.

  26. Nestor :

    Date: June 24, 2011 @ 9:34 pm

    I have a 2008 Nissan Armada. I gave my son a boost and touched the jumper wires together briefly. Now my air conditioner/heater does not blow cold or hot air out. It does not even blow air to defrost the front windshield no air at all. Could it be a blown fuse? I open the hood and the air conditioner pipes are cold and frozen so it seems that it works just not blowing.

  27. jSlentz :

    Date: June 27, 2011 @ 10:27 pm

    My corolla’s a/c does not come on when you first start the car but after the car runs for about 10 minutes you can feel the motor bog down and the a/c kicks on and the air conditioning blows cold air. Any suggestions?

  28. dennisb - Auto Tool Sales :

    Date: June 28, 2011 @ 6:57 am

    J, I would check at the compressor to see if the clutch is getting power and NOT engaing when it should. Also a scan tool and a wiring diagram may be needed to see what’s going on. Sorry, no silver bullet to fix this one. May need to do some manual electrical circuit and controler testing. Good Luck.

  29. Jimmy :

    Date: July 10, 2011 @ 10:15 pm

    My 2003 Toyota Camry has a button that you push to turn the AC on. The AC will run for a little while but then the light on the button starts to blink and the AC blows warm air. Any idea what this could be?

  30. dennisb - Auto Tool Sales :

    Date: July 11, 2011 @ 6:44 am

    Jimmy, usually on a Toyota this means that the AC compressor’s clutch COIL (Electro Magnet which engages the clutch) is failing. I would check to see if the coil is getting power and ground to it when the problem is occuring. If it is not, there could be an open circuit before the coil in a connection or pressure switch. A wiring diagram and working knowledge of the system may be required to diagnose if it’s not simply a coil that is failing. Good Luck.

  31. Lee :

    Date: July 14, 2011 @ 11:24 pm

    my 06 cobalt does not blow cold i added freon to the low side because the gauge would not fit on the high side, does it matter which side u put it in? and it reads 35% you can hear the compressor going but no cold air what could be the problem?

  32. dennisb - Auto Tool Sales :

    Date: July 15, 2011 @ 6:43 am

    Lee, low freon is the leading cause of an A/C system NOT cooling in cars – however it’s not the ONLY reason. You really need both side pressure readings to help diagnose the problem. See the “Adding Freon to Car AC – Gauge Readings Explained” article which is linked at the bottom of the article above.

    AC do it yourselfer chaging hose for car.

    See step #1 in the article above regarding which service port to use when just adding refrigerant with a do-it yourselfer kit. The reason the kit is designed to ONLY fit the LOW side is in an attempt to make it “Idiot Proof”. Car makers have TWO different size service ports to help prevent someone from having a refrigerant can blow up in their face. If charging with a freon can was done on the HIGH side with the system running, the 200-300 psi could burst the can! Good Luck – Be Safe.

  33. Jerry :

    Date: July 17, 2011 @ 4:26 pm

    I have a 2006 Lancer ES. The A/C blows cold for 20 minutes or so, then the compressor shuts down. After watching it for a while, I noticed the following: Low side pressure is 35 psi at idle and will drop to 15 psi at around 2500 rpm (100 degree ambient temp). I suspected low pressure was causing the cut-out, so I set the fan to low and watched the pressure drop to about 20psi (I don’t have a guage to measure discharge pressure). Then I revved the engine to get the pressure to around 10 psi when the clutch disengaged. Now, the static pressure is at 150 psi at an ambient temp of 100 degrees. The clutch will not engage. I set a jumper to the switch at the sightglass to see if the problem was there with no success. If it kicked out on low pressure, then, at what static pressure will the LP switch reset? What should the static pressure be? In a couple of hours, it will work fine again for 20 more minutes.

  34. dennisb - Auto Tool Sales :

    Date: July 18, 2011 @ 8:53 am

    Jerry, without both side gauge readings it’s hard to guess what the problem may be. See AC Gauge Readings Explained for more info on your questions about readings.

    Since the AC does blow cold (when it’s working) it most likely has the correct amount of refrigerant. I would check gauge readings, make sure the cooling fan is on when it’s suppose to be and verify that the coil is being energized appropriately. My guess would be that there’s a condenser fan issue, expansion valve, coil cutting out or a switch could be faulty. Good Luck.

  35. Ron :

    Date: July 18, 2011 @ 1:35 pm

    I replaced my compressor and evaporator (poured 8 oz of PAG150 oil per Comp mfg directions. I am ready to vacuum the system down. Will the vacuum suck the oil back out?

  36. dennisb - Auto Tool Sales :

    Date: July 18, 2011 @ 1:56 pm

    Ron, you probably are already aware but – usually it’s also recommended to turn the compressor shaft 10 times prior to starting the car after installing a replacement compressor with oil. The compressor cannot “compress” oil, so damage could occur.

    To answer your question, if the service ports are not located near the compressor, I wouldn’t think any oil would be removed with the pump.

  37. Craig :

    Date: July 19, 2011 @ 4:20 pm

    Just put compressor accumulator and orfice tube in a 2001 expedition with rear air. It’s aprox 97 degrees in Tex. My gauges are reading 49 on low side and 265 on the high side at idle. With AC on max cold and both front and rear fan speeds on high. Idling at 1500 rpm for 5 minutes front center air vent reads 60 and rear bottom side vent with control on floor reads 67.
    This morning with temp of about 85ish front vent was as low as 38 and easiely in the 40’s for awhile but when things warm up so does the AC. Just noticed when I turn the front blower controller to low temp out of vent temp lowers to 40 degrees in about 2-3 min. Rear vent down to 62 degrees in about 8-10 minutes.
    AC line going into condinser measures @ 146. Top of accumulator measures 88 degrees
    Thanks in advance for you thoughts
    Craig B

  38. dennisb - Auto Tool Sales :

    Date: July 19, 2011 @ 5:54 pm

    Craig, the low side seems a little high – however… Vehicles with rear A/C are sometimes more tricky to diagnose. The is because the readings are based on front and rear components. For instance, you may have similar readings to what you have now but the rear expansion valve could be closed and the rear AC not cooling any. So you have to take in consideration that slightly altered (or inaccurate) readings may be what you’re dealing with.

    The rear AC hardly ever gets as cool as the front on any vehicle. Everything is further away from the condenser and compressor so there’s more efficiency lost by the time the refrigerant travels that far.

    Ambient/Outside Temp can effect effficiency.
    When it’s 97 degrees outside, the inside temp could easily reach 130-140 degrees. Therefore, it will most likely take longer than 5 minutes for it to cool off the passenger compartment. Remember the air inside the vehicle is not the only thing that has been heated up in the mid-day Sun. Feel the dash panel and you’ll see what I mean. Dark vehicles hold heat even more. Owners of black cars usually have this complaint in Southern states in the summer. With your’s, I would watch the thermometer placed in the dash vent and see when it stops getting cooler. With it 97 outside 55-60 would be great. As far as lower temps being measured with the blower on lower speeds; that is normal. The air flowing through the evaporator naturally gets cooled more when there’s a lower amount of air trading/transfering heat and cold with the evaporator. Good Luck.

  39. ralfy :

    Date: July 28, 2011 @ 2:05 am

    When i drive in city it will not cool but when on freeway it cools the car great any ideas?

  40. dennisb - Auto Tool Sales :

    Date: July 28, 2011 @ 6:25 am

    Ralfy, common causes of the problem you described are.

    1. Condenser/Radiator Cooling Inoperable (not enough airflow across condenser) Could also be dirty condenser fins but not as common.
    2. AC Compressor not pumping sufficiently. Compresser may only be pumping enough when it is spinning faster at higher engine RPM’s.

    See our other AC articles for more information, especially the A/C gauge reading explained. Good Luck.

  41. lindsay :

    Date: August 23, 2011 @ 4:37 pm

    My 06 chevy cobalt has slowly been showing issues with the ac. A week ago when we turn the car on, the ac kinda made a whinning noise but still. Blew cold…after driving for 10 minutes, well…now the ac just blows out hot air no matter how long we drive. We have tried adding freon but it won’t take anymore. The compressor continuously kicks on and off, usually meaning it has no freon…but I’m assuming since it won’t take any freon, its full. Help…any suggestions or an idea on what the problem is!?

  42. dennisb - Auto Tool Sales :

    Date: August 23, 2011 @ 8:04 pm

    Lindsay, low freon is one cause of the AC not cooling well. More isn’t always better! You may want to see some of our other articles on AC servicing, especially the one about AC gauge readings explained. Good Luck.

  43. cat :

    Date: August 26, 2011 @ 5:06 pm

    Why would my 2005 Mercury Montego, with only 19,000 miles need a new A/C compressor? Could inoperation for 2-3 months during desert heat cause this?

    Dealer added Freeon last summer ran fine until now. Runs cooler at faster RPMS on freeway. Can’t afford $1,300.00 for new compressor. What else might it be? Help, please.

  44. dennisb - Auto Tool Sales :

    Date: August 26, 2011 @ 5:33 pm

    Cat, unfortunately low mileage does not insure a perfectly working AC system. In fact, sometimes NOT driving a vehicle is worse on a car than regularly driving them. Seals in the A/C system are lubricated when the refrigerant flows through the system. The oil is suspended in the refrigerant and travels throughout. Lack of operation means poor lubrication and “dry seals”. The symptom of “Runs cooler at faster RPMS on freeway” usually means one of two things. 1. Low airflow through the condenser. Or 2. The compressor is pumping insufficiently. Sounds t like the dealer has determined the latter. You may be able to get a lower cost repair at an independent shop. Ask about the parts and labor warrantee and if parts are new or rebuilt. Compare apples to apples and choose the best solution – you can have your AC purring like a kitten. Good Luck.

  45. Rei Baloy :

    Date: September 14, 2011 @ 1:42 am

    Dear Mr. Dennis,

    I have Ford Windstar 1999 3.8 and I had my A/C charged with freon at the A/C workshop tech. It’s blowing cold air nicely but I noticed that my compressor is not automatically kicking on and kicking off. It continuously runs without disengaging. This caused my engine overheat. What would could to be the problem. Please help… Your prompt reply is greatly appreciated. Thanks and regards.. Rei

  46. dennisb - Auto Tool Sales :

    Date: September 14, 2011 @ 6:37 am

    Rei, the AC is not likely to cause an engine to overheat. Also, if the engine overheats, the AC will not cool well. I would check the engine overheat problem separately from the AC. First, the AC clutch cycles on and off to prevent freeze up of the evaporator. So as long as the AC is cooling well as you said, I wouldn’t be concerned with it not cycling like you expect it to. It may cycle less dependant upon several factors, but again if it is cooling as it should don’t worry. Second, I would determine if the engine is actually overheating. Since the AC still blows cold, I question if it’s really overheating. Sometimes the gauge can be incorrect, leading you to think the engine is overheating. If there are no other indicators that the temperature is too high, I would check the data screen with a diagnostic scan tool. The vehicle’s computer references engine temp. from a different sensor than the temperature gauge in the dash. This will help to determine if the reading you’re seeing on the dash is correct or not. If the temperature readings don’t match, the sending unit or dash gauge may be faulty. If both readings are indicating an overheat, then check for a reason for the overheat. But as I said, the AC is NOT likely to cause the engine to overheat. Good Luck.

  47. Rei Baloy :

    Date: September 14, 2011 @ 7:10 am

    Thanks Mr. Dennis for the prompt reply. Hence, as far as the engine overheating is concerned.. yes it overheats when I switched ON the AC. I’ve noticed just after I parked the car after running on the huge traffic on the road. The water coolant comes out from the plastic water reservoir tank. Usually, the normal position of my temp. guage is on half position (50%) but, during that time time it raised up to (80%). However, when the AC is OFF the Engine doesn’t overheat even it’s running on huge traffic or idle for an hour. Could there be a problem on my engine then? Could it be the cooling system (i.e radiator is having a problem likely clogging or corrosion)inside on it? Once again, thanking for your help… actually it gives me relief on the other part about the AC compressor. Thanks and best regards. REI

  48. dennisb - Auto Tool Sales :

    Date: September 14, 2011 @ 7:22 am

    Rei, As I was saying the AC is not going to cause an overheat. It will however increase the demand on the cooling system. I would check the cooling system for leaks, proper flow and cooling fan operation. Once the cooling system is working properly you’ll be OK. Good Luck.

  49. Rei Baloy :

    Date: September 14, 2011 @ 7:30 am

    Dear Mr. Dennis, Acknowledge with thanks receipt of your prompt reply… I’ll go to the radiator/ cooling system mechanic to check proper flow and cooling fan operation. Thanks for the big help…More power.

  50. udai :

    Date: October 18, 2011 @ 12:24 pm

    my car ac initially works but after some time when i switch on it wont work though the compressor works. Ac gas is full. What could be the reason.

  51. dennisb - Auto Tool Sales :

    Date: October 18, 2011 @ 12:28 pm

    Udai, if I were checking it I would first see what the low and high readings are when the problem occurs. See our AC gauge readings explained for more information. Good Luck.

  52. Chuck C :

    Date: October 31, 2011 @ 8:59 am

    I know I have a leak in AC line on 2000 F150. I added 2 cans of R134a this summer. This morning the heater was blowing cold air. Are the 2 problems related?

  53. dennisb - Auto Tool Sales :

    Date: October 31, 2011 @ 9:06 am

    Chuck, not related. Most common cause of the heater not working is low coolant. See our blog on heater blowing cold air for more information. Good Luck.

  54. Onyeka :

    Date: November 1, 2011 @ 9:38 pm

    I have a ’96 Accord whose AC clutch rubber got burnt. On removing the pulley, it was discovered that the coil was also burnt. All the burnt items were replaced. The compressor wasnt touched. Then when switched on, the compressor makes some rubbing noise. The gas was evacuated, compressor oil added and gas refilled. the AC started cooling real good though the rubbing noise remained. After driving about 3km to a mart, on starting the car the AC no longer blows cold air. On the small window on the can-like drier, i could see the gas bubbling and the lines attached to the drier were very cold which I was told shouldnt be so. I was told debris from the compressor may have gotten into the drier and blocked it and I need to change the compressor and drier. What do you suggest please.

  55. dennisb - Auto Tool Sales :

    Date: November 2, 2011 @ 6:38 am

    Onyeka, the compressor starting to “lock up” or otherwise fail most likely caused the clutch components to overheat. The burnt clutch was an indicator that the compressor was having a problem. The rubbing noise is most likely the compressor making excess noise because of internal parts worn and not turning smoothly. Regarding the drier being cold, yes it is unusual for it to be cold (on your model) since it is normally hot to the touch. Remember HIGH pressure means HIGH temperature and LOW pressure means LOW temperature. So the theory that debris is blocking some flow in the drier causing low pressure and low temperature is plausible.

    I would disassemble the system, removing the compressor drier and expansion valve. Flush the remaining components in the system and consider adding an in-line filter. Then install a new compressor assembly (clutch components already on it), drier and expansion valve. It’s important to have the correct amount of refrigerant oil in the system and follow the compressor installation instructions – which includes turning the compressor by hand 10 times to displace the oil before operating. Evacuate the system (pull a vacuum with a vacuum pump) for at least 15 minutes and recharge the system. Good Luck.

  56. Kyle :

    Date: November 3, 2011 @ 2:06 pm

    I’ve been teaching my technicians steps like these for when the summer comes upon us. I have Kansas City area auto repair stores and the summer months can be brutal on the A/C. Flushing the components and checking expansion valves are a must. There are so many steps, it seems daunting sometimes.

  57. cmoua :

    Date: November 3, 2011 @ 2:17 pm

    I have a 97 Honda Accord. Recently I notice that the ac is not cooling well. At initial start of the a/c, it’d cool down to the low 50s deg and then it’d cycle back up and stay around 60 deg. It doesn’t matter if the car is idlying or going fast on the hwy, the temp stays around 60 deg. The condensor fan and radiator fan is working properly. The system was evacuated and recharged to the correct amount of R-143 but I still get the same result. Could it be a weak compressor or a bad expansion valve?

  58. dennisb - Auto Tool Sales :

    Date: November 3, 2011 @ 6:51 pm

    Cmoua, I would check gauge readings to help diagnose the problem. I would also check the heater valve (if it has one). If a heater valve or a blend door is not fully closing, the heater will make the temperature climb some. Good Luck.

  59. Rob :

    Date: November 28, 2011 @ 6:47 pm

    I have a 2001 Hyundai Santa Fe. I just replaced the freon about a month ago. Suddenly the other day it started blowing hot air again. Everything is running ok and the lines look good. What do you think happened-Thank You

  60. dennisb - Auto Tool Sales :

    Date: November 28, 2011 @ 7:30 pm

    Rob, I would check the gauge readings and go from there. Good Luck.

  61. castie :

    Date: January 22, 2012 @ 3:22 pm

    HI Dennis, i have a quick question. Air started blowing warm recently. I recharged it myself but FORGOT to turn the AC on while doing so. I have the blower on full blast but neglected to turn the actual ac on. Naturally it is still blowing hot air. Should i do it again correctly or do i need to take it into the shop?

  62. jenn h :

    Date: January 24, 2012 @ 5:20 pm

    So my A.C. is making this funny noise. Sounds like the fan may be hitting something. Also it isn’t blowing cold air at all. What should I do?
    How much does it cost to have a computer tell me what the problem is?
    Tried putting freon in it but its still full so wasted 10 on a can of freon for nothing.
    This sketchy mechanic tried to tell me it was the compressor. And he would charge me $878 and change to fix it.
    I was like ‘nah, man. I’m good.’
    I don’t believe it’s the compressor due to the fact I bought the car in 2009 its a 2007 and only has had myself and an elderly person as an owner. In which neither of us have used the hell out of it for something major to be wrong with it.

  63. dennisb - Auto Tool Sales :

    Date: January 24, 2012 @ 6:21 pm

    Jenn, sounds like the compressor is most likely the problem. By checking the gauge readings your mechanic or you can determine if it’s pumping sufficiently – the mechanic you mentioned may have already done this. No computer or scan tool needed just low and high readings and knowledge of what those readings mean. That’s why we have a tech article on AC Gauge Readings Explained linked above. Regardless of who is driving the car, things fail. I’ve seen compressors fail on two year old cars with less than 30,000 miles. It’s not hard to imagine a bad compressor on a five year old car that makes noise in the engine compartment, doesn’t blow cold air and wasn’t low on refrigerant. It’s best to go by the readings though and see where exactly that noise is coming from. Good Luck.

  64. Rob :

    Date: February 4, 2012 @ 11:50 pm

    Turned out it was not a leak. I opened up the cabin filter area and the door that holds the cabin filter was broken. All the air was rushing under the glove box but never made it to the vents. I put some cold stuff in and it works like a charm. Now I am having trouble with a slight acceration problem that doesnt throw a code. It never ends!

  65. dennisb - Auto Tool Sales :

    Date: February 5, 2012 @ 7:43 am

    Rob, glad you figured it out. I have seen that before, on several Chrysler 300’s. Their cabin filter door is directly above where the right front passenger’s feet would be. If that door falls, air will rush out instead of being directed through the evaporator core. The airflow through the vents will be greatly decreased also if that happens. Good Luck with your acceleration problem, we have more articles that may help… feel free to look around.

  66. Juan :

    Date: February 26, 2012 @ 9:41 pm

    My car a/c turns on and cold air comes out of a/c when car is running, the faster you go the more cold air comes out. As soon as you stop, air stops blowing cold. A/C pipe in engine compartment is cold and when air comes out cold. It only comes out cold when set to normal a/c. On max a/c and auto a/c it doesn’t blow no matter how fast you drive. I was told it was a part that needed to be replaced but they needed to drain something to get to it. I forgot the name of the part. Any ideas?

  67. dennisb - Auto Tool Sales :

    Date: February 27, 2012 @ 6:54 am

    Juan, sounds like an expansion valve possibly, since you say that something needs to be drained. The refigerant has to be recovered anytime the expansion valve is changed. If it were just an electrical control component the refrigerant wouldn’t have to be recovered (or system emptied). Good Luck.

  68. Brad :

    Date: March 15, 2012 @ 8:31 am

    In the past 2 years i have noticed that every summer i have to recharge my 2008 nissan versa hatchback. This year the air pressure was at 0, and my AC wouldn’t even turn on until i charged it for a little bit. It works great and blows wonderful cold air. I assume that i have a leak in the system. Should i get a flush of my system or just have an auto repair shop find the leak and fix it?

  69. dennisb - Auto Tool Sales :

    Date: March 15, 2012 @ 11:57 am

    Brad, your Nissan definitely has a leak. A flush does nothing to fix a leak. Usually a flush is just to remove contaminants from a system, especially when replacing an A/C compressor.

    Using UV dye or an electronic leak detector are the most common ways to find a leak. We have a related A/C article on pinpointing the source of leaks. If you are interested in trying to locate the leak yourself check that page out linked at the end of this article. Otherwise I would recommend taking your car to a shop for diagnosis. Good Luck.

  70. Chris smith :

    Date: April 19, 2012 @ 1:33 pm

    I have a 2004 Dodge Dakota 3.7L…the lower AC pipe has frost on it but the condenser feels warm.and I dont hear that click sound when running AC…would this be just a fuse

  71. dennisb - Auto Tool Sales :

    Date: April 19, 2012 @ 2:03 pm

    Chris, a blown fuse doesn’t make sense. I would check the gauge reading and then determine what’s wrong. See our AC Gauge Readings Explained article for more information.

  72. Chris smith :

    Date: April 19, 2012 @ 5:45 pm

    OK Dennis I just found out that my problem was low Freon,but when I hooked-up can it would only hook-up to high point which was the condinser.everything seems to be working Ok now,but have One more question…what is the best R34 to use..they sell so many???

  73. dennisb - Auto Tool Sales :

    Date: April 19, 2012 @ 5:57 pm

    Chris, like in this article and other directions you will read anywhere, charging is only to be done on the LOW side.

    R134a is R134a no matter what brand it is. Unless you are getting something from Mexico that may not be regulated like in the states.

    Stay away from the products with stop leak because it may damage your seals and clog the condenser or other components. Good Luck.

  74. Chris smith :

    Date: April 19, 2012 @ 6:06 pm

    Thanks for all your help Dennis, but the fitting would not hook-up to the low side at all,just the condenser it would… I have a 2004 dodge Dakata 3.7L, so thats odd to me that the fitting would not hook-up to the low side….. Have you seen this before?

  75. dennisb - Auto Tool Sales :

    Date: April 19, 2012 @ 6:15 pm

    Chris, if using an AC manifold gauge set only charge through the blue hose which will be the low side. Simple charging kits are meant to be sort of idiot proof by ONLY providing the LOW side fitting. This prevents someone from hooking up to the high side at all.

    Many low side service ports or fittings are located on the accumulator near the passenger side firewall.

  76. Lisa :

    Date: April 26, 2012 @ 11:58 am

    Approximately how much should it cost to replace the speed controller for my AC, 2002 Lincoln Cartier

  77. dennisb - Auto Tool Sales :

    Date: April 26, 2012 @ 12:06 pm

    Lisa, prices vary greatly. I don’t have access to labor guides like I used to because I sell auto tools full time now – I was a Master Auto Tech in the field for over 25 years. I would call around to several local shops for a price comparison. You may also want them to verify the issue, because if it doesn’t fix the problem you may be left holding the bag. Good Luck.

  78. Kris :

    Date: May 1, 2012 @ 9:55 am

    I have a 1993 bravada. i replaced everything envolving the a/c encluding a new compressor. a shop vaccumed the system and charged it up.The compressor was pre charged with oil but the mechanic told me to add oil to it then turn the shaft faced down.It only blows cold when driving 20mph+ but heats up when stopped at idle. pressures are 39 psi on low side and 255 high side. I also installed a new fan clutch. I put 8 oz. of oil in the compressor. Could there be too much oil in it?

  79. dennisb - Auto Tool Sales :

    Date: May 1, 2012 @ 10:17 am

    Kris, too much oil could cause a problem. Usually compressors that come with oil have enough for it by itself. You can drain and measure if there’s any doubt. Normally I would add a couple of ounces for each additional component that is replaced, like the drier, an evaporator etc. Go by factory recommendations for best results.

    I would also check to make sure the coolant fan is working as it should since you say it cools well when driven past 20 mph. If there’s not enough air flow across the condenser the temperature will rise. Good Luck.

  80. Danny :

    Date: May 9, 2012 @ 3:10 pm

    2000 Oldsmobile Alero, replaced leaking high side line along with accumulator since it was a very humid day when replacing line. Had shop vacuum down system and I added appropriate amount of freon per sticker on radiator grill. System worked ok for the first few days but not as cold as was prior to line failure. Now no cold at all, system is still charged. Lines going to evaporator coil, smaller line is very cold larger line coming out is same temp as outside. Compressor is running and all appears ok except the line coming out of evap coil is not cold at all and no cold air is coming out of vents. If the evap. coil is clogged would the compressor still appear to be operating normally.

  81. dennisb - Auto Tool Sales :

    Date: May 9, 2012 @ 3:23 pm

    Danny, I would check with gauges to see what the high and low readings are and go from there. Good Luck.

  82. Danny :

    Date: May 11, 2012 @ 8:02 pm

    Dennis, checked pressure with my manifold gauges and low is measuring 30, high 50. The compressor is running, the only explanation is a bad compressor, yes? It is just weird since the compressor is not squealing and never did make any strange sound. It also worked previously prior to changing out the 2 hoses coming off the compressor. I think I made a grave error when I was charging the system after I vacuumed it down. I had a 30 oz can of R134a and held the canister upside down while charging instead of allowing the air to go in naturally. Would this be a compressor?

  83. dennisb - Auto Tool Sales :

    Date: May 12, 2012 @ 8:26 am

    Danny, the readings of 50psi (high side) on your 2000 Oldsmobile Alero isn’t what it should be. If that reading is accurate, it seems the system is under-charged. If the compressor wasn’t pumping sufficiently you would have a reading on the high side closer to 80-100. I suspect there’s a leak and the system is under-charged. Especially when replacing components, a leak detector should be used to make sure here’s no leaks. Sometimes, dish detergent soap can be used at hose connections to check for leaks and to make sure all is sealed properly.

    I would check the pressures with the system off. This is called static pressure. Both sides should be around 80-100 psi. The reason the low side seems about right (when the system is running) is because the compressor is most likely a “variable displacement” type which maintains the correct low pressure even if the system is low.

    Incorrect charging could cause damage and the compressor doesn’t have to make a lot of noise to fail. Although, I would do some more checking before condemning the compressor.

  84. cmoua :

    Date: May 12, 2012 @ 3:08 pm


    Now that summer is near and the temperature is rising, I finally took your advice from last year and check the heater valve on my 97 Honda Accord A/C problem. A simple adjustment of the heater valve to fully close the blend door and prevent any hot air going into the vent fixed the problem. Prior to this simple adjustment, the coldest air I get from the vent is 60 degrees. Now I get cold air blowing in the low 40s degree. I just want to thank you for your suggestion and help. YOU ARE AWESOME!

  85. dennisb - Auto Tool Sales :

    Date: May 12, 2012 @ 5:01 pm

    Cmoua, Thanks for letting me know that I helped. I’ve adjusted quite a few of those heater valves on Honda’s over the years. It’s one of those simple things after you know what to look for. Have a great weekend.

  86. sinned :

    Date: May 13, 2012 @ 5:00 am

    please help, i have a yaris 2008 model. my car AC is not working properly. my AC gets cold only if i am idle. but when i drove 20-40speed the cold is gone. -Thank you.

  87. sinned :

    Date: May 13, 2012 @ 5:03 am

    sorry what i mean is when my speed is over 40 my AC blows warm… tnx

  88. dennisb - Auto Tool Sales :

    Date: May 13, 2012 @ 7:51 am

    I would check high and low gauge readings and go from there. Good Luck.

  89. sinned :

    Date: May 14, 2012 @ 3:57 am

    thanks dennis, one more thing, how will i know if the problem in may AC is the compressor? tnx

  90. dennisb - Auto Tool Sales :

    Date: May 14, 2012 @ 6:23 am

    I would use the pressure readings to see if the compressor is pumping sufficiently. See our article on Gauge Readings Explained for more information.

  91. steve :

    Date: May 19, 2012 @ 1:13 am

    My pump turns with the belt but the center part moves on and off like surging what does that mean?

  92. dennisb - Auto Tool Sales :

    Date: May 19, 2012 @ 8:42 am

    Steve, sounds like the compressor is cycling on and off too quickly which indicates low freon and possibly a leak. Good Luck.

  93. Collin :

    Date: May 21, 2012 @ 10:17 pm

    02 cavalier
    A/c was not getting cold
    Replaced orifice tube and recharged
    The compressor is running but the small (high line gets cold) at the orifice tube. Then traces to the fire wall and comes out of the fire wall to the dryer.
    The small line is cold and the larger (low) line and dryer is some what warm. What’s going on here

  94. dennisb - Auto Tool Sales :

    Date: May 22, 2012 @ 6:23 am

    Collin, normally a flush is done after replacing a compressor. You cannot flush a compressor. Cold at the orifice tube is normal. I recommend getting the gauge readings and go from there. Without gauge readings it’s anyone’s random guess. Good Luck.

  95. Sara :

    Date: May 28, 2012 @ 11:35 pm

    I recently bought a 2000 Caravan and found the ac doesn’t work. I bought a recharge kit, added it, nothing happened. I was told that if there is a leak that I would only have cold air for a short time, but I literally had none. When I put the pressure gauge on the low side port I received a 0 reading and that never changed throughout the charging process, when I would stop charging (I bought the kit with a trigger mechanism) the pressure gauge would spin completely around and then stop back at 0. SO this means I have a leak so big its coming out fast as its going in? Wouldn’t I hear/see/smell it?

  96. dennisb - Auto Tool Sales :

    Date: May 29, 2012 @ 6:19 am

    Sara, yes. You should be hearing, smelling and possibly seeing vapor. A common leak is inside the passenger compartment from the evaporator. If I couldn’t get a general idea of where the leak is, I would check with an electronic leak detector while slowly charging the system. Good Luck.

  97. MaryAnn :

    Date: May 31, 2012 @ 2:30 pm

    My air conditioner in my 2005 Mazda 6 i stopped working. A mechanic put a new part for the air conditioner which goes under the hood. I do not know the name of the part but he said when he pushes down on the top of the part the air conditioner works but when he lets off of the part the air conditioner stops working.

  98. dennisb - Auto Tool Sales :

    Date: May 31, 2012 @ 2:35 pm

    MaryAnn, not nearly enough info to go on. Could be a bad electrical connection at a switch or coil. Good Luck.

  99. MaryAnn :

    Date: May 31, 2012 @ 2:45 pm

    I was also told by a different mechanic that the computer was bad and causing the air conditioner problems.

  100. dennisb - Auto Tool Sales :

    Date: May 31, 2012 @ 3:17 pm

    MaryAnn, that would make sense if what the mechanic was “pushing on” under the hood was the computer. I have definitely seen computers that malfunction when slight pressure or slight twisting was applied. That is one way to test. Slight tension applied upon the computer shouldn’t make anything stop working. Think of all the vibration and bumps the computer has to sustain under normal driving conditions. Good Luck.

  101. John :

    Date: June 4, 2012 @ 9:36 pm

    1998 F-150 a/c didn’t work when purchased. Took it back to the dealer and they said they went over the whole unit, compressor, charged system, no leaks. They mentioned there weren’t any blown fuses. Blower blows but not cold air. They mentioned it most likely is something electrical but they haven’t a clue what. Any thoughts?

  102. dennisb - Auto Tool Sales :

    Date: June 5, 2012 @ 6:20 am

    John, If the compressor is not engaging, it may not be getting power to the clutch coil. It could be a faulty control head, switch, relay, coil, an open circuit etc. The mechanic needs an electrical wiring diagram of the circuit, knowledge of the system and an electrical tester like either a multi meter or a power probe. Good Luck.

  103. usman :

    Date: June 6, 2012 @ 6:01 am

    OK, I have a few questions.
    1- How would i know if my condenser is not cloged up from inside? Its clean and neat from outside though.
    2- What’s the purpose of sight glass on the dryer bottle?
    3- Why is it that on evenings and mornings, my car ac works perfectly, but in the afternoon’s, its not so good?

    PS I am from Pakistan and here the temperature is around 40-42 C and yeah that is hella hot…

  104. dennisb - Auto Tool Sales :

    Date: June 6, 2012 @ 7:22 am

    Usman, Wow, I though I had it hot in Florida! For our readers which are more familiar with Fahrenheit temperature readings, 40-42 Degrees Celcius converts roughly to 104-107 F.

    How would i know if my condenser is not cloged up from inside? Its clean and neat from outside though.

    The condenser (located in front of the radiator) can be checked somewhat with an infrared thermometer and looking for extreme temperature differences within a very short span. It is normal to have higher temperatures at he entrance of the condenser and cooler temperatures near the exit and gradual temperature changes in between. Also the gauge readings may indicate a restriction in the condenser.

    What’s the purpose of sight glass on the dryer bottle?

    The purpose of the sight glass originally was for indicating a low charge of refrigerant. Years ago, I was taught that if there were bubbles passing through the sight glass, the system was low. Do not relay on this 100%. This is just one indicator and I’ve learned long ago from hands on experience that a few bubbles are totally normal. If refrigerant is added until all bubbles are gone the system will surely be over-charged! One good use of the sight glass is to see if the system has UV dye in the system without taking anything apart. Also if the system has burnt, contaminated in the system, it’s easy to see. The oil and refrigerant passing through the system should be clear or fluorescent yellow/green and NOT brown or black.

    Why is it that on evenings and mornings, my car ac works perfectly, but in the afternoon’s, it’s not so good?

    In my experience, the best a car’s AC system can be expected to provide around 40-50 degrees vent air. This may vary depending on the outside (ambient) temperature, how much radiant heat is being passed on through the vehicle etc. Radiant heat also varies depending upon the color of the vehicle. A black vehicle is very hard to cool because of all the extra heat gained from the heat passed through the exterior into the passenger compartment. A white vehicle reflects much of the Sun’s heat in comparison. So, it makes sense that in the mornings and evenings when the ambient temperature is lower that the AC system seems to be working better.

  105. usman :

    Date: June 7, 2012 @ 12:04 am

    wow that was quick responce,thanks mate..
    for the record,40-42 is in my city,there are cities with 50 C these days..thanks to all global warming :p

    our mechanics here are not educated and they learn with age,i mean hit and trial a very stupid thing they do is
    1-remove the thermostat valve for which they think will keep car temp normal..(STUPID RIGHT? ) i have thermostat valve in my car though ..
    2- they take the pipes going to the heater off thinking it will help in better cooling… which i also think is stupid cuz there is button inside cabin to tell if you want hot air or cold air :p

    but as you are an expert,maybe you can shed some light on the two of many stupid things we live here with in me country 😉

    cheers !!!

  106. dennisb - Auto Tool Sales :

    Date: June 7, 2012 @ 6:43 am


    The thermostat is to help the car reach normal operating temperature quickly. Since it’s usually so hot where you are, the thermostat will likely stay open after the car is running for just a few minutes. Removing the thermostat will not make the car engine run cooler except for these first few minutes.

    Removing the heater hoses and not running coolant through the heater core might make a slight difference (cooler) in the air conditioning only because there will be no chance of heat transfer from the heater core to the conditioned air in the passenger compartment. One drawback that I can imagine in systems that use a HVAC door and not a heater (water valve) to control the heater, is that the engine will not benefit from the extra cooling capacity. The heater core is like a small radiator, so the coolant runs through it, the coolant is cooled some.

    If I was working on cars in your very hot climate I would look into adding extra cooling fans if possible to help cool the radiator and condenser. Auxiliary transmission coolers may help reduce heat transfer also. If I had a vehicle with a thermostatic sensor in the evaporator case I would experiment with changing it’s location away from the evaporator slightly in an attempt to reduce the vent temp slightly. In any climate it’s a good idea to keep the condenser clean and to change the cabin air filter (if there is one) to help the system operate as efficiently as possible.

  107. usman :

    Date: June 8, 2012 @ 1:46 am

    thanks mate..appreciate your responce…
    good day!!!

  108. Jim :

    Date: June 9, 2012 @ 7:22 pm

    Hi ,
    I have a 2002 T-bird. The AC does not blow cool at an idle, it’s fine at anything abouve 1500-2000 rpm though. I put a gauge on the low side at it’s over 110ps at idle on those cheap lowside charging kit gauages.WHen you rev it up tp 1500 -200RPM or so the low side goes down to 50 or so and blows clod. SO it works fine on the highway, sucks in the city. This was on a 90 degree day. Will buy a set of mainifold gauges to look at the high side tomorrow. Please oh please let this be a bad compressor and not the TXV valve.

  109. mark d :

    Date: June 9, 2012 @ 9:07 pm

    Hi how are you? I added refrigerant to my 2006 Subaru forester and 10 min after I added it something by the engine started to squeak only when the AC was on and it blows out warm air. When I just start the car and am driving over 50 it will blow cold air for about 3 min and then goes back to warm air the whole time.please help I don’t no what could of happened.

  110. dennisb - Auto Tool Sales :

    Date: June 10, 2012 @ 7:26 am

    Mark, sounds like you over-charged the system. I would check the readings, low and high. You will most likely need to take this to a shop and have the excess refrigerant recovered. Good Luck.

  111. Barry :

    Date: June 13, 2012 @ 5:40 pm

    I have had a a/c line in a 1998 jeep Cherokee 4.o get a hole rubbed into it and leaked all the freon out. Do I need to put anymore oil in the compressor before I put on the new lines?

  112. dennisb - Auto Tool Sales :

    Date: June 13, 2012 @ 6:49 pm

    Barry, it’s impossible to know exactly how much oil to add without going to extremes. I.e. taking components off and draining them one by one etc.

    I would look for evidence that oil was lost (surely some was). I may also look in the compressor and drier to get an idea if there was sufficient oil in the system already. In most cases, adding 2-4 oz should be enough as long as the area of the leak wasn’t drenched. Just don’t go over-board, because too much oil in the system can cause issues. Good Luck.

  113. sinned :

    Date: June 17, 2012 @ 1:54 am

    hi dennis, i have tottaly changed my car compressor – my car is Toyota Yaris 2008. my mechanic change the compressor with corolla compressor. it works very fine its almost a month now. but i just obeserved recently that after driving contineous 100km/h for 05mins and over. my AC blows poor air a bit noisy, even i put it to maximum.. but the cold still there, only the blowing of air goes down… but if i slow down to 70-80km/h the air starting to blow high. pls help. thanks.

  114. Will :

    Date: June 18, 2012 @ 2:48 pm

    Hi dennis I have a 2002 nissan altima. I charged my ac about 30,000 miles ago I use the ac alot almost always on. Now my ac blows cool but not like before. It works then blows outside temperature then goes back to blowing cool. What could this be leak, freon or compressor?

  115. dennisb - Auto Tool Sales :

    Date: June 18, 2012 @ 2:58 pm

    Will, sounds like the system is low again. When the system is low the compressor will cycle off and on more frequently until the system is so low that compressor will not come on at all. I would check the high and low readings and go from there. Good Luck.

  116. Will :

    Date: June 18, 2012 @ 3:02 pm


  117. james :

    Date: June 19, 2012 @ 3:28 pm

    I have a 2001 GMC Sonoma, re charged the ac but still blows hot air, noticed the gauge jumps to warning and also my heater doesn’t blow hot air, both stay at a warm temp.

  118. dennisb - Auto Tool Sales :

    Date: June 19, 2012 @ 4:16 pm

    James, I would check for the cause of the engine overheating – most likely a coolant leak. After the engine is running at a normal temperature, the AC has a chance of working if it’s not over-charged now (since you’ve added). Good Luck.

  119. Vern P :

    Date: June 19, 2012 @ 4:37 pm

    I have a 2004 acura tl, about 3 years ago, I had my radiator replced due to damage, a year following that my ac wasnt working, so I had my condenser replaced, everything was great until this year. Now my ac blows cold air sometime, any advice

  120. dennisb - Auto Tool Sales :

    Date: June 19, 2012 @ 5:12 pm

    Vern, The old collision repairs may have nothing to do with the current problem. I would check the readings and go from there. Good Luck.

  121. Sheri :

    Date: June 21, 2012 @ 7:56 pm

    I have a Mazda Tribute 2003 6 cylinder that is blowing out hot are through my AC. How do I know if I need freon or a compressor or something else?

  122. lakay :

    Date: June 25, 2012 @ 1:44 am

    Hi, I am stuck with my car AC again. after a 20 minute drive my AC start to slowdown. Then no more air is coming suddenly air flow is gone. At that moment I stop and checked under my hood. The pipe is freezing. Please advise what to do.

  123. Sinned9 :

    Date: June 25, 2012 @ 3:24 am

    After an hour of driving I pulled over and popped the hood. The A/C line was totally covered with frost from the firewall to the jar shaped thing (covered in frost) attached to the fender and also just as frosty from there to the engine. The air going inside my car is VERY little (almost none). The small amount of airflow that was entering the cabin of the vehicle through the vents, was cold. Until system off turns off the system, and after 15 or so minutes, A/C acts normal for about 30- 40 minutes and the cycle repeats – please Help..

  124. dennisb - Auto Tool Sales :

    Date: June 25, 2012 @ 6:24 am

    Lakay – Sinned, sounds like their is a restriction or the expansion valve is not letting the right amount of refrigerant to flow. I would check gauge readings and an infrared thermometer to help determine the problem. Good Luck.

  125. Melissa :

    Date: June 26, 2012 @ 11:48 pm

    Our 2006 Chrysler 300C recently started blowing cool air, not cold air. I purchased a recharge kit at Auto Zone, added the refrigerant, but then it started blowing hot air, not even cool air. I went back to Auto Zone to ask them what happened and they told me that it could take up to 3 days for the system to blow cold air again, depending on the amount the car is driven and the AC in running. Is this true?

  126. dennisb - Auto Tool Sales :

    Date: June 27, 2012 @ 6:29 am

    Melissa, this is simply NOT true. If the problem was only a “low” refrigerant charge and you added the correct amount the system would blow cold immediately. The problem as I see it, is that we don’t know what the issue was because no gauge readings were taken. Just adding Freon does not help for instance if the system is full but the compressor isn’t pumping properly. Or the system is full but the condenser fan motor has failed etc. You get the idea, that there are many things that can cause a system not to blow cold air besides just low Freon. See our article about gauge readings explained for more information. Good Luck.

  127. Yanitza :

    Date: June 29, 2012 @ 12:57 pm

    Hello, I have a 2000 ford focus. When I purchased it in Oct. 2011 the A.C was working. But now when I click on the A.C button and put it on high, the A.C. turns off for some reason. But when I put it on low it stays on but doesn’t blow out cold air nor enough air. Can you help me?

  128. dennisb - Auto Tool Sales :

    Date: June 29, 2012 @ 1:27 pm

    Sounds like two different issues. Usually the blower not blowing on one or more different speeds indicates a bad blower resistor. With the AC not blowing cold, there’s a good chance there’s a leak. I would check the system with gauges after the blower speed problem has been resolved. Good Luck.

  129. Heather :

    Date: June 30, 2012 @ 6:54 pm

    Hi, I have a 2002 Suzuki Car. When driving normal speed AC blows cold air, but when sitting at stop light or driving slow warm air. The coolant has to be refilled every month because it is all gone. Have taken it to mechanic and they say I don’t have a coolant leak. They put on a new air compressor and water pump. Worked great for a month then same problem again. They put on ANOTHER new air compressor FREE this time and it worked great for a month, now same problem again! They say it has plenty of Freon and coolant. I am wondering why my coolant is all gone and has to be refilled so often if there is no leak? Could a leaky head gasket or and electrical problem cause this AC problem to happen over and over? What should I have them check? Please help! I don’t understand why it works for a month or so everytime they fix it then the same problem comes back! Thanks.

  130. dennisb - Auto Tool Sales :

    Date: July 1, 2012 @ 8:49 am

    Heather, the car’s engine needs to be running at normal operating temperature for the AC to wok properly. The coolant leak could be from a head gasket. I would do a carbon test to check for the presence of exhaust fumes in the cooling system. Also would take a close look at the radiator cap. Sometimes if the radiator cap will not allow coolant to return from the coolant reservoir properly, leaving the cooling system lower and lower over time.

    As far as the AC system, after the engine overheating issue has been resolved; If the problem persists, I would check with an electronic leak detector and UV dye to find the refrigerant leak. When the vehicle overheated previously, it’s possible some refrigerant was expelled from the relief valve and if it did not close properly it could leak. So, I would pay special attention to the high pressure relief valve when checking for leaks. Good Luck.

  131. Lisa :

    Date: July 3, 2012 @ 12:53 pm

    I have a 2000 Blazer with an AC problem. It will blow cold for about 10 minutes, then only blow hot. Sometimes it will get cold again after a while, but I try not to drive long distances in the heat, so I don’t know if it would continue to go cold/hot/cold/hot.

    When it’s cold, it’s very cold.

    I also have an issue with the blower. It will blow on level 4 (Highest) all the time, but only on the 3 lower levels if my car is accelerating. I don’t know if that has anything to do with the hot/cold, or is just a different issue with the same general area, the AC.

    Any help would be appreciated!

  132. dennisb - Auto Tool Sales :

    Date: July 3, 2012 @ 1:24 pm

    Lisa, sounds like two different issues. I would check for power and ground at the AC clutch coil when the AC stops blowing cold. Might be a bad clutch coil. The blower issue sounds odd to me. Usually if the blower only works on high the resistor would be bad, but it’s strange that it would blow when accelerating. I would recommend checking for power at the the blower motor and go from there. Goods Luck.

  133. Lisa :

    Date: July 3, 2012 @ 5:43 pm

    Thanks Dennis.

    I’m not so worried about the fan speed, I’ve learned to live with that and I can put it on High and distribute the air between head/feet, so that it’s not too much air. But, I figured I would mention it, since I didn’t know if it had anything to do with the cooling issue.

  134. Teresa Small :

    Date: July 7, 2012 @ 1:55 am

    I’ve had my condenser and my compressor replaced. And all leaks checked and fixed. The readings were taken and done how it should be done. My AC works great when it’s cooler out. When its hot it will blow cold when I’m driving. I can hear a vacume noise right before it gets real cold. Also the two middle vents blow colder air than the two side ones. What can the problem be?

  135. dennisb - Auto Tool Sales :

    Date: July 7, 2012 @ 10:33 am

    Teresa, the system may be slightly under-charged. I would check the AC pressure readings with an AC manifold gauge set. I would look at high and low side readings (see our AC Gauge Readings Explained). The sound you hear is most likely not vacuum, it’s probably just the Freon flowing through the evaporator as it is supposed to. Sometimes the sound can be louder than normal if the system was not on the vacuum pump long enough, or if the system is low on charge. Good Luck.

  136. JC :

    Date: July 7, 2012 @ 10:27 pm

    Hi,I have a 2000 VW Jetta and basically the A/C doesn’t work, initially the compressor was bad. I went and changed it and after I changed it, refilled the system. It was blowing cold air, but the next day was only blowing hot air. I took the car to check for any leaks but the system is fine. Any ideas of what could the problem be?

    Any help would be appreciated!


  137. dennisb - Auto Tool Sales :

    Date: July 8, 2012 @ 7:25 am

    JC, when a compressor fails it can contaminate the AC system with worn internal parts. When replacing a compressor, the proper thing to do is to flush the system, replace the drier, expansion valve and sometimes even add an extra in-line filter. It’s possible the new compressor has failed due to pumping the garbage in the system. I would check the pressure readings and determine what the problem is. See our AC gauge readings explained article for more information. Good Luck.

  138. hi :

    Date: July 8, 2012 @ 7:30 am

    I tried to recharge my ac because it had a leak in the compressor but I forgot to turn on the ac while doing it ! Please help.

  139. dennisb - Auto Tool Sales :

    Date: July 8, 2012 @ 7:37 am

    Normally the refrigerant won’t flow into the system unless the compressor is on (unless an AC machine is being used). If the Freon came out of the can into the system quickly for you even though the AC wasn’t turned on, I suspect there’s a large leak. I would use an AC manifold gauge set so I could see the readings and check the system with an electronic leak detector. Good Luck.

  140. JC :

    Date: July 8, 2012 @ 4:10 pm

    Hi Dennis and thanks for the prompt response, so you think the compressor failed because something got stuck in the system? Also how can I tell if the compressor has failed? I know the clutch does engage when I turn the A/C on.


  141. dennisb - Auto Tool Sales :

    Date: July 8, 2012 @ 4:33 pm


    I would check the pressure readings and determine what the problem is. See our AC gauge readings explained article for more information. Good Luck.

  142. Rick :

    Date: July 9, 2012 @ 12:16 am

    Hi have a 96 camaro 3.8l
    Removed compressor, flushed system and blew it out several times. Residual solvent kept coming out and seemed like it was never going to stop (then was told I wasn’t supposed to be flushing the expansion valve and the hose with the orifice tube). So I pulled off the hose coming from the bottom of the condenser and more fluid leaked out – several oz. Blew out the lines a few more times, replaced compressor, pulled vac, waited 45 min – no leaks. Added less than 12 oz of refrigerant before the low side registered around 45 psi which seemed odd. The high side is around the same psi but they flucuate slightly. Needless to say, my efforts yielded no cold air. I did NOT replace the orifice tube because I couldnt find it. Any advice? Id REALLY appreciate it thanks!

  143. dennisb - Auto Tool Sales :

    Date: July 9, 2012 @ 7:01 am


    It’s true that an expansion valve cannot be flushed. In addition, an orifice tube and compressor also cannot be flushed. On the 1996 Chevrolet Camaro, an orifice tube is not used. It has an expansion valve located on the evaporator near the firewall on the passenger side – under the hood. See image below.

    Any time a compressor has failed, it’s a good idea to replace the expansion valve. The flush is a good idea also, but as you have found out it takes some effort. Also if flush solvent is left in the system the compressor can be damaged. That’s one reason why there are A/C Flush Machines that make this job easier for repair shops.

    Always replace the drier before vacuuming the system down and recharging.

  144. Xavier :

    Date: July 10, 2012 @ 9:53 pm

    Hi I have a Lincoln Aviator that i take to shop every year to add freon but my problem is that when its cooling a bad smell comes out of the vents speciality when fan is in lowest I took it to a couple places and they drain system and vacuum it, recharge freon but still same. Any suggestions?

  145. dennisb - Auto Tool Sales :

    Date: July 11, 2012 @ 6:37 am

    Xavier, Sounds like two separate issues. The fact that you need Freon added every year means there’s a leak. See our article on finding refrigerant leaks for more information.

    Regarding the smell, that most likely is not Freon. Freon is almost odorless, especially if there is only a very small leak. Probably mold. Most Aviators have a cabin air filter, I would change it. I would also spray Lysol disinfectant spray or a similar product into the air return located under the passenger side dash (with AC on recirculate or max). This will kill bacteria / mold that is likely causing the smell.

  146. Diana :

    Date: July 11, 2012 @ 10:32 pm

    I had a friend lookat my 06 Mitsubishi Galant because my AC only blows hot air. He told me the compressor needs to replace but that without his discount it’s only $130 at advanced auto parts. But everywhere we look it’s $400. I tried to check and see if he sure it was the entire compressor, but we had a falling out. Do you have any clue what he might have meant or why there is such a difference?

  147. dennisb - Auto Tool Sales :

    Date: July 12, 2012 @ 6:29 am

    Diana, Aftermarket parts cost less, but you do want to make sure you are comparing “like” products. I would check with the parts store for details. However, it may not be a bad idea to get a second opinion on the diagnosis of the problem to begin with. Good Luck

  148. Robert :

    Date: July 13, 2012 @ 5:06 am

    I have a 2004 Hyundai Santa Fe blowing warm air and compressor is not coming on. If I add freon to the system, how do I get the compressor to turn on to suck the freon out?

  149. dennisb - Auto Tool Sales :

    Date: July 13, 2012 @ 7:28 am

    Robert, Once the system senses some pressure in the system the compressor will come on automatically. Good Luck.

  150. George :

    Date: July 16, 2012 @ 8:18 pm

    HI Dennis, I have 2005 Chevy Cobalt it blows warm air it has freon I installed gauges low side reads 40 psi and the high side reads 150 psi to 200 psi. I hear the compressor kick in so whats the problem?

  151. Lola :

    Date: July 17, 2012 @ 7:03 pm

    I noticed a couple months ago that my A/C was not very cold so I took it to my mechanic to see if he could add refrigerant. He checked it out and told me the compressor was going out and would need to be replaced. My mechanic said my car was full of refrigerant and there was no room to add more. I have a 2003 Mazda Protege and spent a lot of time deciding if I wanted to fix it or buy a new car. I decided to fix it since my car runs great. The A/C worked well for a week. I noticed it kind of started working less well. Finally two days ago, it started blowing out warm and hot air. It had never done this before I repaired it. Now my car is in worse shape. I am taking it to my mechanic. He said it most likely was a leak. My concern is why would my car be leaking refrigerant when it wasn’t before? I don’t know if I should give this mechanic the benefit of the doubt or if he is clueless about what is going on. Please help.

  152. dennisb - Auto Tool Sales :

    Date: July 17, 2012 @ 7:27 pm

    Lola, there’s no way for me to say if your mechanic did a proper diagnosis, if something else failed or if there was a defective compressor. Anything is possible. I would take it back and let the mechanic look at it. Good Luck.

  153. JC :

    Date: July 17, 2012 @ 8:23 pm

    Hi Dennis, i’ve finally tested my compressor and from what i understand there is not enough pressure from the compressor thru the high side, if i remember correctly the mechanic said that it was only 100 psi and needed be around 200 to 250 psi, is that correct, are there any fixes for that other than a new compressor?

  154. dennisb - Auto Tool Sales :

    Date: July 18, 2012 @ 6:17 am

    JC, sounds like the compressor is not pumping. Your mechanic is correct. If the compressor is bad there’s no way around replacing it. Good Luck.

  155. infamous :

    Date: July 18, 2012 @ 9:51 pm

    if my compressor is bad, would the cause my system not to charge? p.s. the compressor still comes on.

  156. dennisb - Auto Tool Sales :

    Date: July 19, 2012 @ 6:20 am

    If the compressor is not working, the system may not accept the charge because the lack of suction. The compressor may come on but that doesn’t mean it’s working properly. Good Luck.

  157. infamous :

    Date: July 19, 2012 @ 9:02 pm


  158. bob :

    Date: July 21, 2012 @ 12:31 am

    I did my ac, I was putting the oil in but forgot to turn on the air. When I turned it on, it snapped then I continued to put the freon in, but it still won’t blow cold air. Did I mess everything up?

  159. dennisb - Auto Tool Sales :

    Date: July 21, 2012 @ 9:01 am

    Bob, I would caution anyone adding oil. First I would only add oil if changing a component or if there was evidence that oil was lost (oil residue). Never use any oil that has stop leak because that can cause more issues (like clogged expansion valves). Excessive oil in a system will cause it not to cool as efficiently as it should. This is because, oil doesn’t have the same properties as refrigerant, so too much oil and not enough refrigerant in a system is not a good thing. If adding oil is necessary, don’t over do it. It depends on the method of adding oil that’s being used and it depends on what components are being changed. Just remember that compressors sometimes can be damaged by having to handle too much oil, all at once.


    Back to your concern. The snap you heard could have been the compressor reacting to too much oil and it not being able to compress it, causing a failure. Or it could have just been the clutch engaging which is normal. I would check the gauge readings to see what the system is actually doing. See our AC article on Gauge Readings Explained for more info. Good Luck.

  160. JC :

    Date: July 22, 2012 @ 10:07 am

    Hi Dennis, I’ve finally replaced the compressor, but here’s my concern, i did not see the guy evacuate the system after he changed the compressor, he did it before, is that right? also, if the compressor was a used one, should i replace the drier too? Thanks

  161. dennisb - Auto Tool Sales :

    Date: July 22, 2012 @ 12:07 pm

    JC, the common term “Evacuate and Recharge” doesn’t really tell the whole story. It really should be called Evacuate, Vacuum & Recharge. So before the system is worked on, the system needs to be evacuated which means recover or remove the refrigerant. After repairs are made the system needs to be pumped down into a vacuum. Then finally recharging means to put Freon back in.


    The drier is supposed to be replaced anytime the system is opened. The descant that’s inside the drier can only hold so much moisture and when the system is opened up and exposed to the outside air it can get saturated quickly. It also acts as a filter keeping contaminants from circulating throughout the system and making it’s way back to the compressor and possibly damaging it. Many compressor manufacturers will not warranty the compressor unless there’s proof the drier was replaced. Of course on a used one, a 30 day warranty is probably all that anyone could hope for regardless of replacing the drier or not. Good luck.

  162. robert bilieux :

    Date: July 22, 2012 @ 12:24 pm

    Recharged A/C and it lasted one day. Had leak before, fixed it with a washer kit on the low side. Tried to charge with stop leak before, only got a cold hand. I could see going in through the clear sight glass. Tried charging with 134A, it did not activate the clutch. Emptied the can but the clutch did not come on. I press valve on both sides-nothing. Bypassing low cutoff switch works clutch engages.

  163. dennisb - Auto Tool Sales :

    Date: July 22, 2012 @ 5:05 pm

    Robert, stop leak may cause other problems (like a plugged condenser or sticking expansion valve). I never recommend anyone using the stuff. The clutch will not engage unless there’s enough pressure in the system for it to safely operate. The fact that the system has no pressure means that there’s a big leak. I would check for a leak and go from there. Good Luck.

  164. Jim :

    Date: July 24, 2012 @ 3:32 pm

    Hi Dennis,
    I have a 02 T-bird. Does not cool at an idle. Abient temp 95F. Static pressre 115.
    At an ide: High = 125 Low 80
    At 200RPM High = 195 Low 50
    Cools fine as long as the RPMs are up. Compressor? AIrflow? I’m hearing these Ford scroll type leak internally

  165. dennisb - Auto Tool Sales :

    Date: July 24, 2012 @ 5:37 pm

    Jim, Sounds like the compressor is not pumping suffiently. The high side isn’t going as high as I would expect with it 95 degrees outside. If it were just an airflow issue (across the condenser) the high side would be going much higher. Good Luck.

  166. Travis :

    Date: July 24, 2012 @ 6:02 pm

    I have a 1997 altima that quit blowing cold air. I took it to a nissan dealer, and after looking at it, they added more refrigerant. It’s still not blowing cold. Does it just take time to work through the system?

  167. dennisb - Auto Tool Sales :

    Date: July 24, 2012 @ 6:39 pm

    Travis, no it should cool right away. Must be a different issue. I would take it back immediately. Good Luck.

  168. Steve :

    Date: July 25, 2012 @ 6:53 pm

    We have 2004 Sienna just replaced cracked radiator . Now, it blows warm air from drivers seat and rear seats vent but cold air from front passenger seat. Maybe coincidence? Could this be electrical problem? Any thoughts? Thanks!

  169. dennisb - Auto Tool Sales :

    Date: July 25, 2012 @ 7:01 pm

    Steve, I would check the readings. With a low charge sometimes there’s a difference in temperatures from various vents. Since the vehicle overheated with the cracked radiator, it’s possible some freon was released through the high pressure relief valve. Good Luck.

  170. Aamir :

    Date: July 27, 2012 @ 7:41 am

    My ac stop blowing cold air out so I went to fill gas up. It worked for a few days and stopped working again. They guy told me I have a leak in the dash board. Is this possible? Please help!! It’s so hot!!

  171. dennisb - Auto Tool Sales :

    Date: July 27, 2012 @ 7:59 am

    Yes, A leak is the most likely cause of what you’ve described (not cooling shortly after putting Freon in). If the leak is in the dash, it’s most likely the evaporator core. Good Luck.

  172. Jennifer P. :

    Date: August 7, 2012 @ 2:36 pm

    We have an 2002 Oldsmobile Silhoutte. The other day I heard a hissing sound come out of the air vents and now the ac is not really working, mainly directed at the drivers vents. The other vents up front seem to blow colder air but it’s not as cold as it could be. What could be the problem?

  173. dennisb - Auto Tool Sales :

    Date: August 7, 2012 @ 3:20 pm

    Jennifer, some hissing sounds in the dash are normal. A vacuum leak may be an abnormal sound, but that’s not what i think you have. Refrigerant traveling through the system can make some sounds. It is possible for the sounds to be slightly more noticeable if the system is a little low. I would check with a gauge set and go from there. Sometimes a difference from vent to may be more obvious if the charge is low. Good Luck.

  174. Kacy :

    Date: August 8, 2012 @ 5:04 pm

    I have a 2005 Mazda Tribute and my ac is blowing hot air. the compressor kicks on and off just fine. I have tried adding the R134A type of freon it takes but still no cold air? Advice please!

  175. dennisb - Auto Tool Sales :

    Date: August 8, 2012 @ 7:05 pm

    Kacy, I would check low and high side pressure readings. see our AC Gauge Readings Explained article for more information on diagnosis.

  176. terry hill :

    Date: August 16, 2012 @ 12:21 pm

    I just purchased a car and do not know the condition of the ac. Anyhow, when the ac is on I hear the compresser turning on but there is no cool air. The car may of sat for over a year never being started. Could the freon have leaked out or do you think there is a leak? What should I do? I dont have money to take it in. Should I refill it and if it stops producing cold air after a while, assume that there’s a leak?

  177. dennisb - Auto Tool Sales :

    Date: August 16, 2012 @ 12:35 pm

    Terry, the only way to know is to hook up AC gauges and see what the readings say. Usually the compressor wouldn’t come on if the system is empty. So it might need a compressor – I would hook up the gauge set and see what the high and low readings are. If you don’t have a gauge set check our site out ( We have some competitively priced. See our AC gauge readings explained article for help in determining what the readings mean. Good Luck.

  178. terry hill :

    Date: August 17, 2012 @ 11:43 am

    Thanks for your reponse. But wanted to add one more thing I found out. I told you that I heard the compresser turning on and it does. However, after runing the car for about 4 minuites (or should it take longer than that to cycle off) I noted that it never turned off. It continuly runs without ever turning off. I know that you said it will not turn on if there is no freon but what about when the compresser always stays on.

  179. dennisb - Auto Tool Sales :

    Date: August 17, 2012 @ 11:49 am

    Terry the compressor may not be pumping – only turning. Without the gauge readings it’s anyone’s guess. Good Luck.

  180. jerry h :

    Date: August 28, 2012 @ 5:49 pm

    I got to work this morning and heard a sizzling noise like something leaking, thought it could be a small hole in my tire but nothing. Sounded more like it was near my radiator, anyway, on my way home I realized that it was probably my A/C had lost all Freon. Well once home and checking, it seems to be the hose that connects to compressor that has a hole in it. Is it a matter of just adding Freon once hose is replaced?

  181. dennisb - Auto Tool Sales :

    Date: August 28, 2012 @ 5:56 pm

    Jerry, no. The system needs to be vacuumed down with a vacuum pump to remove air and mositure. The drier should really be changed any time the system is opened too. Good Luck.

  182. Vance :

    Date: August 28, 2012 @ 6:43 pm

    I have a 1999 Ford F-150 with a 4.6L
    The heater blower works fine but even when off the vents will seep hot air. Hot air will prevail even when the temp control switch is in the cold position. I have replaced the control switches. The AC does not work either.

    Any clues here as to why my vents are seeping hot air?


  183. dennisb - Auto Tool Sales :

    Date: August 28, 2012 @ 6:46 pm

    Vance, the vents will never be 100% air tight but if there’s heated air coming out all the time I would suspect a broken HVAC door or bad actuator. Good Luck.

  184. Vance :

    Date: August 28, 2012 @ 7:33 pm

    Thanks Dennis.
    Ill look into both.
    That is, when I figure out where they are both located. Google here I come!

  185. Vance :

    Date: August 28, 2012 @ 8:15 pm

    hmmm, not much luck on Google.
    Is the temp door actuator the same thing as the Blend door actuator.

    If so, is the actuator near the blend/temp door?

    I think that they may be located inside the cab behind the plastic center console panel near the floor but what a cluster.

  186. Joel C :

    Date: September 4, 2012 @ 4:48 pm

    When I run the AC on my 1999 Ford Expedition it gets cool but not cold. I went to advanced auto and picked up AC refrigerant 134A. I started up and turned on AC full blast and waited 3 mins, then I connected AC refrig into low side port, the gauge on AC showed that the freon level where it should be per the guage. Know I do understand that gauge isnt perfect but it makes me wonder if freon level is ok and maybe I should look elsewhere for the problem. Ideas for me? thanks

  187. dennisb - Auto Tool Sales :

    Date: September 4, 2012 @ 6:16 pm

    Joel, I would check both readings. See our article on understanding the pressure readings to help diagnose. Good Luck.

  188. chris brown :

    Date: September 6, 2012 @ 2:54 pm

    Dennis, i have an 03 jetta that was making a noise and the air was not blowing as cold then over a period of time the noise stopped along with blowing cold air. now it just blows hot all the time. i had it vaccummed and recharged with freon and also checked for still did not blow cold. what could be the issue?

  189. dennisb - Auto Tool Sales :

    Date: September 6, 2012 @ 4:33 pm

    Chris, I would suspect the compressor failed. By checking the pressure readings it would be easy to tell. See our gauge readings explained article for more information. Good Luck.

  190. Amber :

    Date: September 9, 2012 @ 8:41 am

    Dennis, Our ’06 Scion xb has been having problems with the ac for years. The AC stopped working about three and a half years ago, taking it to be recharged. It only worked well for about four months until it stopped again, finally getting us to take it to Toyota to get it fixed. They said ther was no leaks or problems, and just refilled it. (There HAD to be a leak since it was empty again!)
    so since then, we have been living with a very tempermental machine, because another five months, it stopped working again but in a weird way.

    I know AC takes a minute to come on, so it does likenormal. That is until you even try to go over 45mph. It works moderately well under that speed, but once over it stops. Having to brake makes it seem like the fluid moves back to the valve that pumps it, and it works again for the seconds until your over 45mph again.

    The AC has also begun a loud squeaking noise starting aboit a year and a half ago, always only when it starts for the first two minutes or so or until we idle at a light. (we have tested it starting and idling by pressing the AC button when it happens. It starts and stops the noise when done)

    Its going into a different mechanic this Tuesday for a different reason, should i bring up the problem again?

  191. dennisb - Auto Tool Sales :

    Date: September 9, 2012 @ 11:55 am

    Sounds like it could have been over-charged making it cycle off at higher RPM’s due to excessive pressure on the high side. I agree that there has to be a leak. The noise now most likely is the compressor. Throughout the years if oil was never added – just refrigerant alone, the compressor could have been operating low on oil making it worn and noisy now. Good Luck.

  192. Amber :

    Date: September 9, 2012 @ 10:30 pm

    Thank you, I appreciate the help! Wish I had more time to look at the compresser myself, but its the husbands car so its gone for 10 hours a day! :-)

  193. Jennifer :

    Date: September 14, 2012 @ 8:38 pm

    My air only worked on high power for Honda accord. It was really cold so we replaced blower motor resistor and
    Now all levels work 1-4 but it’s
    Not cold like it was. What could it be

  194. Jennifer :

    Date: September 14, 2012 @ 8:42 pm

    Also I just got it out of the
    Shop yest to make the air blow out of the
    Vents because u could hear it
    But it never came out. I relized those mechanics are dumb. So that’s why we replaced resistor today and I was so happy that all levels worked until it wasn’t cold but it’s
    Not hot either just like warm air. I appreciate any advice!!!

  195. Kenneth :

    Date: September 28, 2012 @ 7:16 am

    I have a 98 Acura lt when i turn on the ac the cooling fans go off and the compressor does’t come on.I have check for a short and found none. all the relay have been replaced, and there are no bad fuses. HELP!!!

  196. dennisb - Auto Tool Sales :

    Date: September 28, 2012 @ 7:26 am

    Kenneth, I would start by checking the low and high side static pressures. If the system is low, approximately 50psi or lower the low pressure switch may not allow the compressor to come on. This is for it’s own protection because it’s lubricant is circulated with the refrigerant. If the static pressure is 80-90psi I would obtain a wiring diagram and trace the circuit starting from one end to the other (switch to compressor). Good Luck.

  197. Pedro C :

    Date: January 31, 2013 @ 2:17 pm

    I want to know why my ac will run on the first time I try it on but the second time I try to it doesn’t work. The back AC works but not the front. Any ideas what it may be. i have a Chevy suburban?

  198. dennisb - Auto Tool Sales :

    Date: January 31, 2013 @ 2:52 pm

    Pedro, could be a blower issue if the air stops blowing. Could be an expansion valve problem if it blows, but just not cold. Good Luck.

  199. Scott :

    Date: April 8, 2013 @ 5:58 pm

    Hi Dennis, great article. I read the comments but still am not sure what problem I have. I own a 2004 Explorer – air blowing warm. The blend door actuator is working fine. When the air is on, the compressor did not run at all. I bought a recharge kit, turned the car on, air on max, turned the dial to ambiant temp and pulled the trigger. When I started filling, the compressor kicked on and would cycle on and off. I filled until the pressure was in the filled zone, but the compressor would not run after I stopped pulling the trigger. I didn’t want to damage the system so I stopped there. A day later I decided to try and fill it again by forcing the compressor to run by shorting the relay. So I shorted the compressor clutch relay – started the car, turned air on max and verified that the compressor was running. I connected my can of refrigerant to the low side and pulled the trigger but nothing happened. The pressure gauge didn’t even move. Would you mind telling me what you think could be the issue?


  200. dennisb - Auto Tool Sales :

    Date: April 8, 2013 @ 7:16 pm

    Scott, my guess would be that there is a very fast refrigerant leak. The low pressure switch will turn the compressor off to protect the system when the charge/pressure is too low. You may damage the compressor by jumping the switch or has you have done “shorting the relay”. I would use a gauge set as outlined in the AC Gauge Readings Explained article. And use a refrigerant leak detector to find the leak and go from there. See an article on finding leaks by clicking the following – Find Refrigerant Leaks. Good Luck.

  201. jackie :

    Date: April 8, 2013 @ 7:44 pm

    I just had freon put in my car and they said it wasnt holding the charge but its not leaking from anywhere either…..any ideas on why it wont stay in?

  202. dennisb - Auto Tool Sales :

    Date: April 8, 2013 @ 9:08 pm

    Jackie, there’s obviously a leak if it’s not staying in. When they say it’s not leaking anywhere, that is inaccurate. They just haven’t detected where it’s leaking out. Good Luck.

  203. Scott :

    Date: April 8, 2013 @ 10:06 pm

    Dennis – thanks for getting back to me so quickly. I’ll take your advice and not short the compressor clutch circuit again! I’ll see if I can find a leak – hopefully before it gets too hot.

    Thanks again,

  204. Shawn :

    Date: April 26, 2013 @ 2:24 pm

    Hi dennis,
    I have a 2005 nissan sentra that blows hot air no matter where the temp dial is. The faster I’m going the more hot air is coming through the vents. I went to autozone to add freon today. As I do the vents began blowing cool air. It stayed cool for the next 30-45 minutes (running errands, not long distance traveling) then began blowing hot air again. Am I looking at a leak?

  205. dennisb - Auto Tool Sales :

    Date: April 26, 2013 @ 2:33 pm

    Shawn, sounds like a very fast leak. See our other AC articles on finding refrigerant leaks and AC gauge readings explained for more information. Good Luck.

  206. Vince V :

    Date: May 9, 2013 @ 10:08 pm

    I just got a 1999 Jeep Cherokee. The AC blows but not cold. I added 134a freon to the car with a gauged hose. The gauges read low and then jumped to the red when the compressor cycles. The actual readings were around 25 – 70. The low number raised the longer I did it. I was concerned about the gauges going in the red. The cycling went on about every 5 or so seconds. Is this correct or is there something wrong. Thanks for your help.

  207. dennisb - Auto Tool Sales :

    Date: May 10, 2013 @ 7:33 am

    Vince, you may want to see our article on AC Gauge Readings Explained, linked at the bottom of the article above. But, if it’s jumping to red when the ac compressor cycles off, that would be normal. If it’s too high with the compressor on, the system most likely has been over-charged. If I remember correctly the 99 Cherokee only holds just under 2 pounds of refrigerant. The low side with the compressor engaged should be around 15-30 PSI on your model. Without high and low readings, checking vent temperature, outside temp, engine temp, the condenser fan operation, etc., it’s impossible to provide more information on how the system is performing. Check out the other AC articles for more information.

  208. Malcolm :

    Date: May 28, 2013 @ 6:27 pm

    Our 2007 Chev. Suburban A/C fan started blowing on then off then on again. Worked OK on High until this morning. Smelled electrical short then odometer lights went black and AC setting went from F to C.

  209. dennisb - Auto Tool Sales :

    Date: May 28, 2013 @ 6:35 pm

    Malcolm, sounds like the blower motor was pulling too many amps, burned out the resistor and then finally quit all the way. Not sure what to make of the f to c.

  210. C :

    Date: May 28, 2013 @ 6:36 pm

    2002 pt cruser. added freon with a gauge it was low so i filled it up. worked great for 5 days then i feel cold air out barley feel the air coming out of the air fans…..

  211. dennisb - Auto Tool Sales :

    Date: May 28, 2013 @ 7:24 pm

    I would check for leaks. See our other A/C articles, one specifically on finding AC leaks. Good Luck.

  212. Malcolm :

    Date: May 29, 2013 @ 10:34 am


    Thank you for your prompt reply. Fahrenheit to Celcius on temp. settings.

  213. James :

    Date: June 2, 2013 @ 10:23 pm

    Ok, so heres my situation with my ac. It blows cold air, but sometimes if i turn off the car, come back anywhere from 10-15 minutes to several hours later, it will blow stale air, and wont blow cold air. I had an almost complete ac replacement several years ago, and it started doing it again right after warranty ended. Im thinking there might be a blockage in the ac system somewhere. Someone at advance auto parts told me to try and change out the cabin air filter. I tried, and other than getting a new scar on my finger, that didnt help at all. My car is a 2003 ford taurus.

  214. dennisb - Auto Tool Sales :

    Date: June 3, 2013 @ 7:37 am

    James, The stale warm air would be the result of the AC compressor not pumping when the problem occurs. On the Ford Taurus the most likely cause of the compressor not coming on would be a faulty low pressure cycling switch located on the accumulator. Sometimes tapping on the switch when the problem occurs can make it temporarily work verifying that the switch is the problem. A test light or voltage meter can also be used to see if power is being passed through the switch. Another possibility is the clutch gap on the compressor or a weak coil that engages the clutch. These are the most common causes although there could be other things too. My bet would be on the cycling switch though. I used to keep some for several different applications in my tool box for test purposes because they were so common to fail. Here’s a GM one in the image below that I still had in my box. Good Luck.

    Cycling switch for car AC

  215. MoJo :

    Date: June 3, 2013 @ 9:11 pm

    Dennis, great site and thanks for providing this service. I have an ac issue that I hope you can help me with. I have a 2004 PT Cruiser, 2.4 liter, non turbo. At the end of last season, the ac quit cooling and I have just now started trying to repair this. Static pressure is 85 psi on both low and high side. With ac on max and recirc both the high and low pressure gauges oscillate and then settle on 50 psi for both low and high. Adding a small amount of Freon (less than a fourth of a can) and the pressures go to 85 psi on the low side and 375 psi on the high side. Still only warm air. Any help is appreciated.

  216. dennisb - Auto Tool Sales :

    Date: June 4, 2013 @ 6:38 am

    MoJo, the 85 psi low and 375 psi indicates over charged or low airflow across the condenser. I would check the condenser/radiator cooling fan. I used to replace a ton of those cooling fan assemblies. If the fan is working properly the system is probably over-charged. The system only holds around 1 pound of refrigerant if I remember correctly so it’s very easy to add too much. Good Luck.

  217. camille :

    Date: June 8, 2013 @ 9:07 pm

    I have an 03 Nissan Altima, my husband tried to charge the system but after the low side gets to 22psi (the compressor shuts off, any suggestions of what might be causing the compressor to shut off? Low side gets to 22 psi the compressor shuts off…

  218. dennisb - Auto Tool Sales :

    Date: June 9, 2013 @ 9:26 am

    Camille, I would see what the high side is to get a better idea of what the system is doing. For instance, if the high side is getting up to 450-500 psi and shutting off, it is protecting the compressor from pumping excessive pressure.

    AC Gauge Readings
    Like in the image above, if both sides are too low, that would indicate that there’s not enough refrigerant in the system. If there is a very fast leak the low pressure switch will signal the compressor to disengage to prevent the compressor from being damaged because of no oil/lubrication (which is circulated with the refrigerant).

    Gauge readings indicate possible expansion valve issue.
    In the image above, the low side get’s so low that it eventually goes down into a vacuum. This tells us that most likely the expansion valve is sticking, preventing the refrigerant from re-circulating in the the system. That causes a restriction in the high side resulting in excessive pressure. The high pressure switch signals the compressor to shut down before it is damaged. It causes the low side (or suction side) to go into a vacuum like a drink straw that is bent.

    For more tips on diagnosing gauge readings see Page 2 of AC Gauge Readings Explained.

  219. Dave :

    Date: June 10, 2013 @ 2:37 am

    05 kia sedona and i’ve recently replaced a leaking discharge hose, the compressor, and receiver/dryer. After confirming vacuum was held overnight i recharged the system to 40 oz (2.5 lbs) using 12oz cans and a scale. Air was blowing cold but after a few days it went warm. I noticed that the condenser fan was not coming on so i pulled it out. I applied power directly from battery and nothing, but there were little fragments of plastic from disintegrated conduit tubing all over the place. After a few taps on the ground I thought I cleared the debris and the fan turned on with power. But now two days later I’m back to warm air and the fan is not turning again. Do you think a bad condenser fan motor would explain the warm air? Pressure readings today at 90 degF were 30-35 on low side and about 250 on high.

  220. dennisb - Auto Tool Sales :

    Date: June 10, 2013 @ 7:25 am

    Dave yes. The failed condenser fan motor can definitely cause the high side pressure to go up and the compressor to be shut off. Another indication of a bad fan motor, would be if the AC cools only while driving at highway speed.

  221. Randwick :

    Date: June 16, 2013 @ 10:20 pm

    Great site !!
    I have a 2001 Santa Fe. Just charged the AC which was blowing super cold and correct low side PSI on the DIY kit. But it only lasted a few hours. Looked under the hood and there were fluid remains surrounding the low side port where I had added the coolant. I don’t have the cap, not sure when I lost it. I’ll get a replacement soon.
    My question:
    Is the cap part of the sealing system or do I need to replace the port as well ? Hoping to not waste more AC charges as part of the troubleshooting process.

  222. dennisb - Auto Tool Sales :

    Date: June 17, 2013 @ 12:36 pm

    The service port cap is not intended to seal off the pressure that is present in an AC system. A cap may only slow it down some. It’s common to see a little oil or UV dye at the service port where the refrigerant (not coolant) is added. It is possible however that the service port can leak. Sometimes they can leak really fast if the valve sticks. I would check the entire system with an electronic leak detector to determine where the refrigerant is coming out. Good Luck.

  223. Charro :

    Date: June 17, 2013 @ 3:36 pm

    My girlfriend’s 2005 chevy trailblazer throws only hot air. They put freon three times already and it would work for only that day, and the following day wont work!
    Is there a chance the compressor might be out at all? Or what is the most common parts that leak?
    Any kinda of help would be greatly appreciated!She has three kids, and here in the central valley gets extremely hot in the summer!
    -Thank You! very much
    -Desperate Boyfriend

  224. dennisb - Auto Tool Sales :

    Date: June 17, 2013 @ 6:06 pm

    Charro, sounds like a definite leak – a fast one at that. Compressors are a common problem with GM vehicles when there’s a leak. I would look for evidence of UV dye and also use an electronic leak detector to pinpoint the Freon leak. Good Luck.

  225. LightShow :

    Date: June 25, 2013 @ 10:24 pm

    Hello there. I have a problem with my trucks AC. I did try a DIY recharge kit because my ac freon lvl was low and when I charged it I ended up over charged the system. The gauge ran way into the red and the compressor started turning on and off rapidly. So I panicked and thought the best thing I could do was vent the system some to release the pressure. I did that through the same hose I put the freon in with. I did this before I started reading about it being illegal to do. So I’m sorry about that. Any way I vented what I could so the compressor would stop cycling. It was still in the red. I think I brok the gauge because it went way past the red until it touched the needle on the other side. When I removed the gauge from the system it reads 40 psi in the green with no pressure. So I took the gauge apart and reset it to zero. Tested the gauge on a friends car with working AC and now it reads good again. But when I test my system with the gauge again it reads where it should for the current temp outside. But the system bearly blows any cold air. It blows plenty of air. It’s just not very cold. I’d guess about 5-10 degrees cooler than the outside temp. Which isn’t very much. One thing tho is the more I drive it the better it seams to get. Not real cold or anything but it is working even if it’s bearly.

    So my question is. Where do I go from here. Do I try perging the system and then vac it then try recharging it or did I break something and half to go take it to a mechanic to have fixed instead of fixing it my self? Can you lay out every likely posibility for me please. Should I buy the gauge kit that can read both high and low at the same time? Will that help me fix this in some way? Thank you for any help you can give. Thank you.

  226. dennisb - Auto Tool Sales :

    Date: June 26, 2013 @ 7:29 am

    I understand wanting a quick easy fix. But as I explained in the article above there are many possible reasons for the AC not to cool properly besides low refrigerant. As far as being able to lay out every potential problem and or solution; that’s beyond the scope of what’s possible to provide here, especially with very limited information and not working on the car myself in person. It would be like providing driving directions to a specific location without first knowing the starting place.

    As I’ve mentioned several times before, having both high and low AC gauge readings can assist in diagnosing the problem. It’s the starting place, although there may be road blocks along the way. See our article on AC Gauge Readings Explained for more information on what the readings mean. Understanding a system helps in diagnosing problems. Good Luck.

  227. LightShow :

    Date: June 26, 2013 @ 1:36 pm

    Ok. So I need a set of gauges then. And once I get those and use them and get you further information you would better understand what’s going on? Is that correct? I’ve read through all the articles I could fine. Including all the comments posted here. Along with many other sights. And I have yet to come across a problem that’s like mine let alone similar. I’m not in it for a quick fix. I’m just trying to better understand what’s wrong. As a tech yourself I’m sure you all ready have ideas as to what the problem could be just as I do from reading all the information that I have so far. Is there no further information you could give as to a clue of what could be going on? Here’s another question. What would happen if both Gage’s high and low are reading correct while the compressor is ingauged and the condenser (I think that’s what it’s called. The radiator looking devise in the grill of the truck) fan is running like normal but the same problem persists. Would there ever be a time when you would have to perge the system because the freon isn’t vaporized in the low pressure part of the system? Or how about this question. How do you know when the evaporator is no longer Functioning? Or lets say the compressor. Lets say the clutch is in gauged and I can clearly see the compressor working. How would you tell if it’s not turning the freon into a gas anymore? Or not moving the freon through the system? Is the compressor similar to a water pump? Meaning as long as the belt is spinning it’s flywheel that the pump is working and circulating the from? I have so many questions. I may not have been to where I’m going but if I talk to enough people who have I should be able to get there eventually. Don’t you think?

  228. dennisb - Auto Tool Sales :

    Date: June 26, 2013 @ 1:37 pm

    I understand the frustration. Sorry I was unable to help.

  229. Daniel :

    Date: June 26, 2013 @ 1:38 pm

    Hi Dennis,

    I have a 2000 Yukon Denali in very good shape. For some reason, when I have the AC on, it has started blowing out warm air in the front vents but the vent system for the rear passengers blows out very cold air. They work just fine. I was thinking to try a DIY kit, but am wondering is that what I need considering that the air in the rear vents blows out cold air. Please help, any advice will be greatly appreciated. Thank you.

  230. dennisb - Auto Tool Sales :

    Date: June 26, 2013 @ 3:18 pm

    Daniel, this must be a dual AC system. Since the rear blows cold and the front does not, that indicates a bad expansion valve for the front evaporator. Good Luck

  231. Lisa :

    Date: June 26, 2013 @ 8:26 pm

    03 Chevy Suburban, AC not cold garage charged it two days later hot air, told me rear evaporator was bad so we replaced that. recharged it again, hot air again next day. Back to garage charged no leaks detected by morning no cold air…HELP we leave for the beach in two days and would really like to take our Suburban…garage has given up.
    I think

  232. dennisb - Auto Tool Sales :

    Date: June 27, 2013 @ 7:49 am

    Lisa, we don’t know how much Freon was lost in two days, but whatever it was it had to be substantial since it was enough to cause the AC not to blow cold air. We know that it is a refrigerant leak because you said it did cool when you first left the shop after it was recharged again. If this were my garage I would most likely find the leak and fix it for at least a reduced cost since the evaporator replaced was not the major leak, as first thought. The most common leak on the Chevrolet Suburban in my experience has been the compressor itself (seams of housing). Not to say GM evaporators can’t leak, but they are not known to be a common problem. So maybe it was leaking but was not the main leak.

    Being a technician for so many years, I usually defend repair shops because technicians are more likely to understand the whole picture when it comes to mechanical issues. Cars are complex and car AC’s have many components throughout the vehicle with the possibility of more than one problem at the same time. Vehicle A/C’s are not like a house window unit that is easily taken out and the entire unit replaced in ONE fell swoop. However, if the repair shop is no longer willing to work with you and make the repair right; you may want to take the vehicle to the GM dealer to have it checked. Ask them what method will be used to find it, like soap bubbles, UV DYE, Electronic leak detector etc. Ask for a cell phone video for evidence of UV dye being present or better yet the electronic leak detector beeping faster once the leak has been pinpointed. It may be better to have them fix the leak (rather than the original shop). Ask for the old part. And then dispute some or all of the credit card charges for the evaporator replacement that did not resolve the entire problem. Good Luck.

  233. Eddie :

    Date: July 2, 2013 @ 11:30 pm

    I have a 2008 Dodge Charger and my a/c is not working. I charged it with freon but by the next day it had threw it out. I tried a uv leak detector but was unable to locate the leak anywhere. There is also a very heavy freon smell coming from the a/c vents could it be leaking from inside the car?

  234. dennisb - Auto Tool Sales :

    Date: July 3, 2013 @ 6:34 am

    Eddie, sounds like it might be the evaporator which is located in the dash. Evaporator leaks are a fairly common problem with Chrysler vehicles. The UV dye works well except for helping to pinpoint a leak with the evaporator, because that’s the one AC component that cannot be seen (without partial dis-assembly). If the leak is really fast in the evaporator, UV dye may be seen coming out the drain. Good Luck.

  235. Kelli B :

    Date: July 9, 2013 @ 1:09 pm

    Hi Dennisb
    I have a 2007 Nissan Armada…a while back I noticed that the a/c would only blow on one setting. Now the a/c in the rear will blow but the front does not blow unless I am driving and usually driving 35-40mph or faster. What do you think the issue is? Thank you for your feedback.

  236. Tracy N :

    Date: July 13, 2013 @ 11:42 pm

    I have a 2002 BMW that will cool when started,when you stop goes warm,Highway driving stays cool .It seems to not want to cool when outside temp over 85.We checked fans,freon,fuses,everything seems to be in working condition.Thank You

  237. dennisb - Auto Tool Sales :

    Date: July 14, 2013 @ 9:30 am

    Tracy, I would check the actual AC pressure readings and go from there. Good Luck.

  238. Jessica :

    Date: July 14, 2013 @ 4:26 pm

    Hi, I have a 2003 ford windstar. For awhile when stepping on the gas the air will stop blowing through the vents and come out of the defrost vents only. Once letting up on the gas it would blow again through dash vents. Now it blows both hot and cool air. Is this a leak in a hose or the compressor going out? If its a hose leak what’s the best way to find it? My husband said the reading was slightly on the low side but didn’t seen to take in the refrigerant. Where should we start? We’re in Texas with small children and its HOT! Thanks for your time.

  239. dennisb - Auto Tool Sales :

    Date: July 14, 2013 @ 7:46 pm

    Jessica, this could be two different issues. The air defaulting to the defrost is most likely a vacuum leak that can be detected by listening for a hissing sound and following the lines or by using a smoke machine. The AC not cooling is best diagnosed by checking both high and low pressure readings. The readings will help determine if it’s a compressor issue or a leak. We have an article on AC gauge readings explained that can help with that. Good Luck.

  240. jessica :

    Date: July 15, 2013 @ 2:41 am

    I have a 2009 nissan versa sedan. My a.c stopped working. I can hear the fan working .. but no air comes out. I replaced the sensors thinking that might resolve the issue. On the nissan versa ac knob has . When it does work when you move the switch to 3 you can hear the ac fan get louder. It wouldn’t do that before. Now I have no a.c . Sometimes it works sometimes it doesn’t
    ..please help me and throw me a scooby snack 😉

  241. dennisb - Auto Tool Sales :

    Date: July 15, 2013 @ 7:58 am

    Jessica, can’t think of any sensors that would affect the fan (also called the blower for the inside the car). If the blower works only sometimes, it may just be failing. When the problem is occurring I would check for power and ground at the blower to verify. If the blower motor is getting power and ground supplied and doesn’t work it will need to be replaced. Good Luck.

  242. Moedogz1 :

    Date: July 16, 2013 @ 3:44 pm


    I have a 2000 expedition and i changed the condensor on my truck and added coolant to it and it still blows hot air also the line where u check to see if you have coolant get’s very hot when adding coolant do you think the system needs to be cleaned ?

  243. dennisb - Auto Tool Sales :

    Date: July 16, 2013 @ 4:30 pm

    Would need to know gauge readings after the system was vacuumed down and recharged to the correct capacity of refrigerant. If the service port is getting hot that means high pressure, which is normal on the high side but not on the low side.

  244. Kimbaroo :

    Date: July 17, 2013 @ 10:33 pm

    I have a 2002 Highlander. After adding the refrigerant I noticed the can said to have the car and AC unit started prior. Now my car make a noise when I turn the AC on and when I use the gas. I also noticed that as long as I am driving the AC blows cool, but it takes a while to get cool but the slower I drive or sitting still it’s not as cool. Can you give me an idea on what it might be? Its really frustrating especially now that its summer.
    Thank you

  245. dennisb - Auto Tool Sales :

    Date: July 18, 2013 @ 7:52 am

    Kimbaroo, yeah incorrectly charging a system can cause damage to the compressor. And sometimes without knowing the high and low gauge readings we are just taking a stab in the dark. That’s because it’s not always a “low freon” problem to begin with. And how would you know if the system is now overcharged without knowing the readings?

    So my best guess without having the benefit of knowing any readings just the symptoms, is that the system is overcharged and the compressor is making noise because of excessive head pressure. Which goes down a little when more air is blowing through the condenser cooling fins, bringing the pressures down. More’s not always better. Check out our article on AC gauge readings explained for more info. Good Luck

  246. Kim :

    Date: July 19, 2013 @ 3:39 pm

    I have a 05 E-450 shuttle bus 6.0L diesel, front and rear ac. It cools but not good, i traced out the ac lines and found a site glass and when system is running there is air in site glass. I added 2 cans of 134a and seems to be warmer now at idle and not as good down the road. guage readings are also higher now, however the system holds 4.5LBS of freon, and still air in siteglass,,, any suggestions.

  247. dennisb - Auto Tool Sales :

    Date: July 19, 2013 @ 5:18 pm

    Kim, you can’t go by the site-glass 100%. It’s not intended to be used to gauge how much to charge a system. I would go by the pressure readings. You may have over-charged the system. Dual systems are a little more tricky also. I would take temperature readings from the front and back vents. Don’t expect the rear to cool nearly as well as the front though. If it has been over-charged the system will need to be recovered, recycled, vacuumed down and recharged. Good Luck.

  248. Doug :

    Date: August 5, 2013 @ 11:05 pm

    My 2000 model express van will not take any 134a and I know there is none in it what’s up? What’s something I should check and how? On the low side I pressed in the valve to see if any 134a was in there but none came out and it won’t take any.

  249. dennisb - Auto Tool Sales :

    Date: August 6, 2013 @ 7:25 am

    Doug sounds like when you hook up the AC manifold gauge set you are not opening the valve on the left which is the blue – low side. You should see the pressure gauge go up once the freon is allowed to flow. If you are using a do it yourself kit and not an AC manifold gauge set like we recommend, I would suspect something not working with it (maybe get a new one or better yet, a proper ac manifold gauge set). Good Luck.

  250. brandon :

    Date: August 9, 2013 @ 6:40 pm

    i have an 05 f150 and i bought a uniweld set of gauges with the service adapters. The low side goes on like its suppose to but the high side will not lock on the fitting. So i went ahead and checked just the low side at idle ac off and then full blast. it was 0 both times but was blowing cold air.

  251. dennisb - Auto Tool Sales :

    Date: August 10, 2013 @ 3:43 pm

    Brandon, you may have a bad set of gauges (never heard of uniweld). But, there’s obviously Freon in the system, so you know that 0 psi is incorrect. We sell professional grade manifold gauge sets like Robinair, FJC and Mastercool. Good Luck.

  252. sandra :

    Date: August 11, 2013 @ 10:22 am

    I have a Ford Expedition 200 Eddie Bauer and I filled up the AC and it lasted for a month now it’s back to no cold air. What could the problem be?

  253. sandra :

    Date: August 11, 2013 @ 10:25 am

    Now I took it to get diagnose they said its the ac coil how can that be when the air works fine for about one month

  254. dennisb - Auto Tool Sales :

    Date: August 11, 2013 @ 10:25 am

    The most common problem with AC systems is a leak. See our other articles on AC leaks for more info.

  255. dennisb - Auto Tool Sales :

    Date: August 11, 2013 @ 10:32 am

    The coil could work intermittently, but if it’s low and adding Freon makes it work temporarily, it doesn’t sound like a bad coil. If tapping on the clutch makes it work temporarily work (with changing the 134A level) then I would agree that the coil could be failing.

  256. Mark :

    Date: August 11, 2013 @ 4:43 pm

    2003 turbo PT cruiser. Low pressure hose replaced and system vacuumed, no leaks. Charged with 134a per specs which was 24oz. With AC on full and an ambient temp of 90f. Condenser fan running ok and compressor engaged my low pressure is 44 and the high pressure is 55 with no cycling. The center vent temp is 55f. Both hoses under the hood are cold even the high pressure hose, which seems odd to me. I can regulate the temp from the dash when I drive and the AC will get down to just over 40f if I drive for a bit. Why is the high pressure so low and no cycling?. According to my chart at 90f ambient the low pressure should be 45-64psi and the high pressure should be around 280-300. How can the output air temp be so cold if the compressor pressure is so low?

  257. dennisb - Auto Tool Sales :

    Date: August 11, 2013 @ 6:11 pm

    Mark, the cold lines are low pressure. The PT Cruiser has a factory fill line on the low side that is a high pressure fitting. I’m not sure why they did that. The high side fitting is hard to access on the PT Cruiser – it’s down near the compressor. Used to get scratched up reaching down by the fan to hook to that fitting. Your low side is running too high to cycle off. The common issue with the PT is the fan not working properly. That may explain why the system is only cooling well when the car is being driven and has plenty of air blowing through the condenser. If you can tap on the fan motor and it picks up speed, that would indicate it’s going bad. Good Luck.

  258. Togo :

    Date: September 12, 2013 @ 12:55 am

    Hello Dennis, i have a 99 ford mustang v-6. The problem I’m having is, we had compressor changed and its still doing the same as before, when adding freon it blows cold and fine, but when driving for awhile and stopping in traffic or a drive thru window at idle the freon seems to shoot back out from somewhere around the valve but when driving again it seems to stop and blows cold again. its beginning to be a headache. Can u explain to me whats going on with my a/c system.

  259. amanda :

    Date: September 21, 2013 @ 11:22 pm

    I have a Nissan Versa 2009. My AC won’t blow any air. The AC nor the heater will turn on. I did check the fuses. I can hear the fan working. When it would work the air was cold, so I don’t think it would need Freon. Plz help. I don’t know what’s wrong with my AC and heater. Oh when I turn the knob for the A/C I can hear a small hissing noise.. but no air comes out and the heater makes no noise, if that helps..

  260. dennisb - Auto Tool Sales :

    Date: September 22, 2013 @ 9:29 am

    Amanda, it does sound like an air flow issue. Since you hear the blower that means the motor is good. I would inspect the blower motor to see if the actual blades are turning. The blade assembly on blower motors are round, sort of like a a guinea pig’s exercise wheel. In the auto repair industry (home HVAC also) we refer to them as squirrel cages because of the similar shape of their exercise wheels. This could be broken near the where it mounts to the motor’s shaft, causing just the motor to spin (not moving any air). If the motor and blade check out OK, there could be a door issue inside the HVAC (Heating Ventilation & Air Conditioning) case. The hissing sound you hear could be normal. It might just be the refrigerant moving throughout the system which is normal. But it could be a vacuum leak if the system uses vacuum controlled motors to operate the HVAC doors. So if you cannot access the blower and the vacuum lines if needed, a local mechanic should be able to help. Good Luck.

  261. Bren Terry :

    Date: December 2, 2013 @ 9:46 am

    I bought a 2012 Honda Fit this year that had been on the forecourt for a year. Initially I noticed that the AC would blow warmer air for 2/3 seconds when pulling away from the lights. I took it in to the Honda dealer who checked everything and told me they couldn’t find anything wrong, everything checked out OK. Since then the problem has changed for the worse. Stationary I get cold air but when I’m driving I get a 2/3 second dose of 8 degree warmer air every 18 seconds. I’ve measured it with a fast acting digital thermometer (Snapon). It has been into the garage 3 more times since then, I’ve been out for a drive with their mechanics and shown them the temperature rise on the gauge. Their response was that it was normal for that particular car. I wasn’t happy with that reply so I insisted on taking another car out on a test run but that did exactly the same. My fear is that they are doing something wrong with all the Honda Fits. Could it be model specific or would you suspect something wrong in the system? Your opinion would be much appreciated. The car has a 5 year warranty and I’m loathed to touch it myself but at work we do have a Robinair AC machine we use on our helicopters.

  262. dennisb - Auto Tool Sales :

    Date: December 2, 2013 @ 10:45 am

    Bren, it is normal on modern vehicles for AC compressors to be turned off by the vehicle’s computer during acceleration. This is normally called WOT (wide open throttle) but really just over 20% throttle will turn the AC off. This allows better driving performance particularly on cars with small engines. Vehicles that have larger engines may find that the lapse of air conditioning, is less noticeable because the engine may not require the AC to be off as often or for as long because the engine is not kept at WOT as long. The AC shutting off every 18 seconds, as long as the throttle is applied below 20%, doesn’t sound quite right. The air conditioning system cycles the compressor so that it won’t freeze up. But excessive cycling usually indicates either low refrigerant or the expansion valve restricting the flow too much. Since the system doesn’t hold very much refrigerant and being just a little low can affect the performance; I would recommend removing the refrigerant with the AC recovery machine, vacuuming the system down and putting the correct charge in. This way you will eliminate the possibility of having a low charge, being the cause of the issue. As far as the warranty, this shouldn’t cause a problem. As long as you don’t change any parts, the dealer wouldn’t know anything was done.

  263. JERRY :

    Date: May 29, 2014 @ 7:32 pm

    My 2002 Ford Explorer AC keeps clicking on and off, I put a gauge on it and the reading goes up to 38 psi and immediatly clicks off and drops to 15 then immediately clicks and starts spinning and goes back up to 38 then clicks off and drops to 15 again and keeps repeating over and over, I can hear two clicks, one on passenger side and the other at the pump. diagnoses please.

  264. dennisb - Auto Tool Sales :

    Date: May 30, 2014 @ 8:12 am

    Jerry, not enough information to diagnose. The cycling of the compressor clutch engaging and disengaging, (clicking on and off) is the attempt of the system to average a 28-30 psi on the low side which is normal. We don’t know what the high side is or if the cooling fan is working etc. See our AC gauge redings explained article for more information once both high and low readings are known. Good Luck.

  265. Jason :

    Date: June 3, 2014 @ 4:54 pm

    I have a 2002 Windstar, that I my mechanic did a dye test and saw the compressor was bad. He replaced it with a whole new compressor, dryer, hoses, and all the parts that go along with it. However this the 2nd brand new compressor that has been installed and the system has been taken apart and all the hoses blow out with no success. it has my mechanic frustrated as it happened again today the same day I got it back, and it started blowing freon again

  266. dennisb - Auto Tool Sales :

    Date: June 3, 2014 @ 5:21 pm

    Rebuilt compressors are hit and miss sometimes. Perhaps you can look into a NEW compressor instead of a rebuilt. If you are getting a new one perhaps an OE one from the dealer since you’re having so many problems. Also make sure all the orings or seals are seating properly. Good Luck.

  267. Mike :

    Date: June 5, 2014 @ 12:18 am

    Dennis, I have a 2008 Armada. Ac is blowing but not very cold however, does get a little colder on the highway. Took it to get charged and was told it doesn’t need it. Possible compressor and or expansion valve (ballpark $1200 for both parts and labor). Does this sound legitimate or should I seek a second opinion? Thanks.

  268. dennisb - Auto Tool Sales :

    Date: June 5, 2014 @ 6:33 am

    Mike that sounds plausible based on the sypmtoms. However, not knowing what the readings are I can’t say for sure. I also don’t like that they say “possible”. In most cases the compressor is either pumpimg sufficiently or not. With the exception of some that have internal valving for regulation, the compressor is basically a pump. I would definitely get a second opinion and get the actual AC readings low and high with AC on Max/Recirculate and high blower speed. Note the ambient (outside) temperature at the time of testing and the middle AC vent temperature. Make sure the condenser fan is working correctly and the engine is not running at a higher temperature than normal. Good Luck.

  269. knutsinj13 :

    Date: June 7, 2014 @ 1:22 pm

    99 Corolla re-charged system as directed and now the compressor keeps surging and air is not getting colder I dont know what is causing the surging. Please help.

  270. dennisb - Auto Tool Sales :

    Date: June 7, 2014 @ 4:30 pm

    Most likely over-charged. The compressor will shut off if the high side readings are too high (around 450-500 psi). Not knowing what the pressure readings were before adding Freon and now not knowing what the readings are after adding, makes diagnosing the problem anyone’s guess. Maybe it had a different problem to begin with other than low refrigerant. Adding freon to an already full system causes more problems and can make the system actually blow warmer not colder. I just saw a commercial for a product called “AC Pro” sold at Autozone. It’s a DIY freon adding kit. The commercial shows a couple of guys adding refrigerant without any clue if low refrigerant was really the problem to begin with. It also has stop leak in it which can clog and restrict certain components in the car’s AC sysetem and the repair shop’s expensive recycling equipment. I want to help people work on their systems the right way and when I see products like this marketed to the public as a safe easy fix for any AC problem it’s very frustrating. So my recommendation is to get the low and high side readings and see our AC Gauge Readings Explained article. Good Luck.

  271. buffa :

    Date: June 10, 2014 @ 10:41 pm

    I have a 2010 Nissan Altima and the ac is not blowing cold air. I can turn the clutch by hand so it isn’t froze up, but the compressor isn’t kicking on. Could this be a relay problem, or if not what else could it be besides the compressor?

  272. dennisb - Auto Tool Sales :

    Date: June 11, 2014 @ 8:16 am

    The most common cause for any car’s AC compressor NOT to engage is low refrigerant. If the charge is too low the low pressure switch will not allow the compressor to run. This protects the compressor from running without the lubrication it needs which is circulated throughout the system with the refrigerant. I would hook up a gauge set and go from there. There should be at least 50psi for the compressor to come on some. Usually around 80 to 100psi static pressure (readings without the compressor running) depending upon the ambient (outside) temp. If there’s enough refrigerant for the compressor to run, but it never engages, there could be many electrical issues. Some of the most common problems are pressure switches, high or low. AC clutch coil – which acts as an electro-magnet that engages the clutch disc. It will take some electrical testing and perhaps an electrical wiring diagram and the knowledge of how to read it and follow the circuit for proper testing. Hope this helps. Good Luck.

  273. Tiya :

    Date: June 21, 2014 @ 9:33 am

    I have a 2000 Camry LE sedan. The A/C works fine in the morning, fine in the evening or night, and it starts to work again after sitting out in the rain. But during the day, when it gets hot sitting in the parking lot or driving in stop-and-go traffic, the A/C stops working and the fan blows hot or uncooled air. The A/C switch green light is steady and not blinking.

    The next morning it works fine again. It seems like it also stops working if the cabin temp rises (due to sun) even if the outside temp is moderate (mid-70s). It certainly stops when the temp is mid-80s and above. But if it rained and car got cooled off, it comes on again.

    My long-time (30 years) mechanic said the pressure was too high and he said there was some blockage in the system and he flushed it out and recharged the freon. No difference. Now he says the compressor is acting up and stops working when it gets hot, so I need to change the compressor, the receiver/dryer and the expansion valve.
    He says the A/C switch is fine, thermostat is fine.

    I think it is something that controls the compressor on/off that appears to be temperature dependent, but he insists that the compressor is the one that stops working when it gets hot, because it is old (14 years).

    Is he right? The green light is not blinking, so it is not the magnetic relay. The freon already is charged fully, so it is not low freon. It works fine until the sun heats up the car or driving in stop-and-go traffic.

    Another mechanic said there was moisture in the system, so he replaced the dryer. No difference. He put the old one back and did not charge me anything for that. Then he said the expansion valve was clogged and there was debris in the system.

    Seems like each mechanic is coming up with a different story or “maybe it is this” type diagnosis.

    My longtime mechanic did not say anything about debris or clogged expansion valve. I suppose if we replace enough parts one of them will be the culprit, but it is an expensive way to fix the problem.

    This model year Camry did not have have the A/C system included in its diagnostic computer system, so there is no code reported that the mechanic can check that tells him what part is malfunctioning.

    Please advise. Thank you.

  274. dennisb - Auto Tool Sales :

    Date: June 21, 2014 @ 10:03 am

    I would have left the new dryer on even though it was not causing the current problem. Anytime the system is opened it should have a new dryer because the desiccant will absorb moisture in the air when it’s exposed to it.

    No one can just speculate what the problem is and expect to be right a hundred percent of the time. The vehicle needs to be checked when the problem is occuring. Without having them check the AC system when the problem is occuring, you can ask 10 different AC Tech’s and get 10 different answers of what might be wrong… The best way to get at the root of the problem is to have a qualified tech diagnose the problem when it’s acting up. It could be a high pressure switch malfunctioning or an intermittent open circuit etc. But without checking were just guessing. Trying to diagnose a problem when it’s NOT occuring is a waste of time. We call this “chasing a ghost”. Good Luck.

  275. Tiya :

    Date: June 21, 2014 @ 12:51 pm

    Thanks, Dennis. I must say I am astonished at your fast response (within 30 minutes! Man, you are good).

    The frustrating part is the A/C seems to work when I take in for diagnosis or even if it doesn’t, by the time the mechanic gets it in the bay from the queue, the car has cooled down and it is working again. Collaring the mechanic away from his current car to check out my A/C “this instant” is a problem.
    Anyway, I will try asking him again.

    Asides from all that, is there any truth in his statement “A 14-year old compressor will stop functioning when it gets hot and function again when it cools down.” That is the premise of my mechanic’s diagnosis.

    Thanks again.

  276. dennisb - Auto Tool Sales :

    Date: June 21, 2014 @ 2:27 pm

    I would ask him to explain how the age can cause this to happen, especially if he has not even checked it when the problem was occuring.

  277. Joel :

    Date: June 25, 2014 @ 2:38 am

    Hello, I have a 96 f150 with the 5.0 engine, I’ve been battling this problem for about a year, I’ve replaced the compressor, dryer, orifis tube, and the high pressure line, flushed the entire system. Vacuumed and filled the system and the gauges read where they should and the air blows great then at random times like just when I start the truck or sitting still, or even doing 35 I’ll here a loud pop followed by hissing that I’ve pin pointed to freon escaping thru the high pressure relief valve and can not figure this out for the life of me! Oh and I’ve also replaced low and high side switches. Some days it won’t do this at all, usually take about 3-4 times before I have to refill and start over, any advise would be greatly appreciated! If you could please tell what and how to check. Thanks

  278. dennisb - Auto Tool Sales :

    Date: June 25, 2014 @ 6:44 am

    I would check both low and high side readings and the condenser fan operation. Most of the time when the relief valve has to vent refrigerant, it’s because the high side is getting too high either by being over-charged from lack of airflow through the condenser fins. It’s also possible there’s a restriction but the gauge readings should help determine. Good Luck.

  279. Joel :

    Date: June 25, 2014 @ 8:48 am

    The gauge readings look normal, as far as blockage when I first full the system I let it run for about 30 – 40 minutes everything seems to operate fine, but the compressor run constantly even when I run it on normal air, shouldn’t it kick off every now and then, and shouldn’t the high pressure switch cut the compressor off if it’s getting to the point of blowing the valve open? Checked the condenser and it looks clean and can see thru it, I have a billet grill that’s wide open so should have more air flow than with the factory grill.

  280. dennisb - Auto Tool Sales :

    Date: June 25, 2014 @ 10:57 am

    OK, without me knowing what the actual high and low readings are, I’ll just have to take your word for it that they are normal. Yes, the high pressure switch should turn the compressor off if the readings are too high, around 450-500 psi. So, you’re saying it never gets that high which would indicate that the high pressure relief valve is faulty. This isn’t a common failure but I’ve seen a few bad before. Good Luck.

  281. Joel :

    Date: June 25, 2014 @ 11:21 am

    The reason I replaced the high pressure hose was to replace the pressure relief valve so it’s new also. But it just continued doing the same thing. What I was wondering is there a way to check the high pressure switch and the plug that goes on the switch to make sure it’s getting power and the switch is functioning properly? Sorry to be a bother also the gauges hold steady at about 35 low, 225 high.

  282. dennisb - Auto Tool Sales :

    Date: June 25, 2014 @ 11:40 am

    Joel, no bother. But, I wouldn’t be concerned with checking the power and the high pressure switch. You said the problem was the pressure relief valve letting refrigerant out. I’ll here a loud pop followed by hissing that I’ve pin pointed to freon escaping thru the high pressure relief valve” The relief valve could possibly be faulty (there’s no wires going to it). If it’s letting refrigerant out and the pressure is 225 psi it’s bad. But since you replaced the relief valve with the hose assembly there could be other issues. It’s not likely to have the old pressure relief valve releasing pressure and a new one which apparently was included on the hose assembly you installed.
    AC High Pressure Relief Valve Location
    Sometimes high pressure relief valves are located on the rear of the AC compressors like in the picture.

    My guess is that the high pressure is getting high enough for the high pressure relief valve to release some of the pressure. Yes the high pressure switch should turn the compressor off but the real issue is “what’s making the high pressure get up so high?”. I’d still say the pressures are getting higher than what you are seeing while you have the gauges hooked up. Either over charged or the cooling fan not pulling enough air through the condenser fins are the most likely things that can cause this.

  283. Joel :

    Date: June 26, 2014 @ 1:13 am

    Ok did some more checking, yes I did say the gauges are reading normal when I fill the system and I let it run for several minutes after, but it never does it till after I’ve driven somewhere, but tonight messing with it I had the key on and the engine off and wiggled the plug on the high pressure switch and my clutch started clicking on the compressor so my plug must be faulty I would assume and may have possibly damaged the switch? Could this cause the problem I’m having? Could explain why everything operates fine until I’m on the road vibrating the plug kicking the compressor in and off? Going to change both tomorrow after work and see. What do you think?

  284. dennisb - Auto Tool Sales :

    Date: June 26, 2014 @ 8:06 am

    Joel that’s definitely a problem. But not the problem causing the high pressure relief valve to release some pressure…

  285. chris :

    Date: June 26, 2014 @ 11:56 pm

    I have a 1994 ford ranger and the a/c compressor locked up, I was told by my local auto parts store to get a used 1 and then put in a can of first charge because it contains oil, I changed it with a used 1 and then put in the can till the gauge that came with can said it was at the proper charge but I’m getting no cold air out, the compressor engages & disenngages, and when it does the pressure gauge goes down and then up. Is the compressor bad or did I do something wrong? I can’t afford to go to a garage so is there a way for me check something?

  286. dennisb - Auto Tool Sales :

    Date: June 27, 2014 @ 8:16 am

    Chris, some parts guys at local parts stores are knowledgeable and some are not. I’m a master tech with 30 years of experience in hands on auto repair. When I’m in parts stores I’m amazed on how confidently (an incorrectly) advise customers (sometimes that customer is me) on repairs. See the following article for steps in Changing an Automotive AC Compressor.

  287. Chris :

    Date: June 27, 2014 @ 4:56 pm

    Thank you for answering my question, and the article, I added oil as per the article. After putting all together the compressor wouldn’t engage itself before I added freon, but as soon as I got freon in, it started to engage. Is that normal, or should I take the compressor back and start over. Thank you again for your help.

  288. dennisb - Auto Tool Sales :

    Date: June 27, 2014 @ 5:13 pm

    Chris, I’ve looked the “First Charge” that Autozone sold you.

    First Charge

    This isn’t what I recommend. Not sure how much oil is in it either. It says 12.5 oz. but how much is oil and how much is refrigerant is what’s unclear. If you saw the article and the specifications for the refrigerant level for your vehicle you’d know that it takes 36 oz of 134A for a full charge. The compressor will not engage until there’s enough pressure in the system to prevent damage. This protects the compressor from running dry. I go by specs and an AC manifold gauge set for both high and low pressure readings.

  289. Chris :

    Date: June 27, 2014 @ 6:02 pm

    Dennis, Thank you for your help, you provide a great service here.

  290. Greg :

    Date: June 29, 2014 @ 4:47 pm

    I have a 02 Mazda protege and had the lines vacuumed correctly and freon added correctly and it’s still not blowing cold air it’s like the compressor is not getting a signal to turn on and suggestions?

  291. dennisb - Auto Tool Sales :

    Date: June 29, 2014 @ 5:14 pm

    I would check for power and ground at the clutch coil. Good Luck.

  292. Joel :

    Date: July 2, 2014 @ 2:09 am

    Hello it’s Joel again, going to try to get more detailed with my pressure relief valve problem, when I vacuum and fill the system the gauge run at close to 35 low and 220 high and run in that range smoothly. I can turn the truck off and back on and the gauges will read the same and blows cold air nicely, but if I leave the truck off for an hour both gauges read close to the same pressure at about 90 and when I start and turn the air on the low side goes down slow and the high side goes way too high causing the relief valve to blow, but if I manually turn the compressor on and off before the high side gets too high about 3 times, then it’s starts to work correctly at 30 low and 220 high and works fine until the next time it sits no running, it’s almost like I have to prime it. It’s a 96 f150 with the 302, new compressor, dryer, high side line with new relief valve, new low switch, new high switch, and orifice tube. The orifice tube is red if that helps? Just can’t seem to figure out why this only happens after sitting. System was flushed as well but I would think if I had a blockage that it would not operate at all correctly like I said after having to prime it several times to get the pressures where they need to be it will run fine no problems until I leave it off awhile! Thanks for taking the time to read this.

  293. dennisb - Auto Tool Sales :

    Date: July 2, 2014 @ 7:42 am

    I haven’t ever seen that problem. The only thing I can think of is that possibly there’s too much oil or the incorrect type or viscosity of oil in the system. After it sits, the oil is pooling. When oil has pooled it cannot be compressed, which might explain the high pressures. After the oil gets spread out a bit the system can start to work somewhat normally. That is, until the next time it’s allowed to pool again. Good Luck.

  294. Earnest :

    Date: July 7, 2014 @ 12:06 pm

    I have a 2006 Jaguar S-Type, with a 3.0 V6. I’m experiencing warm air from the AC vents after the engine is warm. It’s fairy cool when I first start up each morning.

    I had the Jaguar dealer replace the Climate Control Module (in the dash) in June of 2013 after having the exact same symptoms of warm air blowing from the vents. But of course to my luck, the $2,000 part/labor job went out of warranty June 4, 2014.

    I’m almost positive my AC is overcharged, as my readings show 55 on the low side (in the red) with the engine running and 98 with the engine off. My research says an “overcharge situation” can also affect the cooling.

    So should I take the car back to the dealership and pay $120 diagnostic fee for them to tell me what I already know and possible get the levels back in correct ranges or is there something I can do to bleed off the excess freon?

    If the Control Module has gone bad again (after one year!!!) I certainly don’t want to shell out another $2,000 on this car.

    Any thoughts would be appreciated.

  295. dennisb - Auto Tool Sales :

    Date: July 7, 2014 @ 12:57 pm

    Without knowing the high side reading, it’s not as easy to guess if it’s overcharged. If the high side readings are also too high, it could be overcharged. It’s also possible that there’s not enough air going through the condenser, or maybe the compressor isn’t pumping sufficiently etc. Whatever you do – please don’t vent refrigerant into the atmosphere.

  296. Earnest :

    Date: July 7, 2014 @ 3:43 pm

    Thanks for the response. If I can find my manifold gauges, I’ll be able to post a high and low side reading. Somewhere in garage. Still looking. And don’t worry, I will not vent the freon into the air. Looks like a trip to the dealer with my checkbook is in the works.

  297. dennisb - Auto Tool Sales :

    Date: July 7, 2014 @ 3:48 pm

    Thanks Earnest. Yeah, we need to leave a little Ozone for future generations. One visual inspection without gauges is to make sure the condenser fan is working. Good Luck.

  298. Hannah :

    Date: July 11, 2014 @ 7:03 pm

    Me and my father bought a 2001 chevy cavalier. The man said he recharges the AC every summer. So we went and bought R-134a refrigerant and filled it to about 30 psi. Well the AC is hardly cold. Its more of a cool air not cold. What should we do. I dont have that much money to fix it if its the compressor.

  299. dennisb - Auto Tool Sales :

    Date: July 12, 2014 @ 10:52 am

    Hannah, see our AC gauge readings explained for information about what both high and low readings should be. The compressor is a common leak with Chevrolet’s but it would take some checking with dye and or a refrigerant leak detector to be sure where the leak is. Good Luck.

  300. david :

    Date: July 21, 2014 @ 5:56 am

    Topped the air con up on my ford fiesta. Was fine however when I reved the engine a little I noticed the compressor kept cutting in and out. Why is this? Cheers Dave.

  301. dennisb - Auto Tool Sales :

    Date: July 21, 2014 @ 7:10 am

    Dave, It’s possible that it’s under or overcharged. Can’t diagnose without the high and low readings. The high pressure switch will turn the clutch coil off if the high side gets too high to protect the compressor from damage from excess pressure. The low side pressure switch will shut the coil power off also, because running the pump (compressor) with too little refrigerant can also cause damage. See our AC Gauge Readings Explained repair article for more insight. Cheers, Dennis.

  302. wallytiger :

    Date: July 26, 2014 @ 5:08 pm

    My nephew’s Honda accord is not blowing AC, so I tried adding a can of stop leak r134 after about 15min it does not appear it is taking the refrigerant.

  303. dennisb - Auto Tool Sales :

    Date: July 26, 2014 @ 5:16 pm

    I would never add stop leak, because it can cause other problems. Also, low refrigerant isn’t always the problem. I would try to add Freon unless I thought the gauge readings indicated it was low. I’d check the gauge readings and go from there. Good Luck.

  304. red :

    Date: August 3, 2014 @ 8:54 pm

    The vehicle sat for 6 yrs but it was working when last used. It’s an R12 system and the AC compressor turning but it wont take charge from my R12 can. Please help.

  305. dennisb - Auto Tool Sales :

    Date: August 4, 2014 @ 8:28 am

    Red, after sitting for 6 years the seals are likely to be dried up and will probably leak. Especially the front seal on the compressor. This doesn’t explain why the refrigerant won’t go in to begin with though. A little should go in without the compressor running. After some starts to go in, the front hub of the clutch should start to engage and disengage. This is called cycling. Since you are getting NO FREON to go out of the can at all, I’d say you are doing something incorrectly. If you are using a simple can tap, perhaps you’re not opening the piercing valve before trying to charge the system. Once you get refrigerant to go into the system, check for leaks, especially the front of the compressor. Good Luck.

  306. jim :

    Date: August 8, 2014 @ 9:13 am

    98 f150 how much on average to repair ac hose that has a leak at a a/c repair shop?

  307. dennisb - Auto Tool Sales :

    Date: August 8, 2014 @ 9:29 am

    Jim prices vary greatly depending on many factors. Which hose, aftermarket or dealer, shop labor rate etc. Could be $175-600…

  308. Katrina :

    Date: August 21, 2014 @ 2:04 pm

    I recharged my 2011 honda civic’s air conditioner and now the compressor keeps shutting off and on every few seconds and the air is hot in the car, could it be over chared and if so is there a way to release some of the freon to fix the situation?
    Please help!!!

  309. dennisb - Auto Tool Sales :

    Date: August 21, 2014 @ 2:35 pm

    Katrina, letting Freon out into the atmosphere is illegal and harmful to the Ozone. I would check the gauge readings and go from there. It could be over charged or under-charged. No one knows without the pressure readings. Good Luck.

  310. robert :

    Date: August 24, 2014 @ 4:44 pm

    My chevy cobalt is barely blowing cold air in the city but once you jump on the freeway it blows cold air .. just when you’re going slow that doesn’t work

  311. dennisb - Auto Tool Sales :

    Date: August 24, 2014 @ 5:07 pm

    Robert. I would check the cooling fan. Also see one of my other articles on the AC only blowing cold at highway speeds. Good Luck.

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  314. Karl :

    Date: May 19, 2015 @ 9:50 am

    Dennis can you please help me? I’m lost. Bought a used 2002 Chevy Cavalier and the ac wasn’t working. Thought perhaps the compressor was bad so I checked it but it operates as it should. Discovered that my ac hose had a hole and leaked out the freon. I replaced the hose and recharged the system. I don’t believe I have any further leaks because the system holds pressure and no more freon loss but the ac still won’t get cold. Any ideas on what my problem is? Thanks in advance!

  315. dennisb - Auto Tool Sales :

    Date: May 20, 2015 @ 3:11 pm

    Karl, I’d check the gauge readings and diagnose that way. Good Luck.

  316. karim :

    Date: June 3, 2015 @ 2:14 am

    I’m working on 01 PT Cruiser and have an a/c problem. We charged the system, but the compressor kicking on but not cold in inside. The high pressure is cold and low side reads nothing. Can you help please? Thanks.

  317. dennisb - Auto Tool Sales :

    Date: June 3, 2015 @ 7:21 am

    Karim. the low and high side pressure readings would tell us what’s going on. From what you’ve said there could be a very fast leak and the system is holding no Freon. I’d check both readings and go from there. If both readings are zero, I’d check for a leak. Good Luck.

  318. JerryC :

    Date: June 13, 2015 @ 12:51 am

    I have a 1997 Honda Accord. Last year the a/c started to periodically quit cooling. I changed a schrader valve and charged the system with guages. Yesterday it quit cooling. The compressor never cycled off. Both lines were warm. The high side was only 125 and low side was reading a vacuum.. I added 12oz of 134 and the high side was almost 200 and low went further in vacuum….-15. Still hot air. Is my a/c compressor bad?

  319. dennisb - Auto Tool Sales :

    Date: June 13, 2015 @ 11:00 am

    Jerry, most likely a bad expansion valve. Good Luck.

  320. JerryC :

    Date: June 13, 2015 @ 1:18 pm

    As a follow up from more reading on your website….could it be as simple as a bad expansion valve? Thks!

  321. JerryC :

    Date: June 13, 2015 @ 1:21 pm

    ok, I just saw your reply. Thanks for the follow up. Is that a half day task on a 97 accord?

  322. dennisb - Auto Tool Sales :

    Date: June 13, 2015 @ 5:02 pm

    Varies, but you would need to have the Freon recovered first. Good Luck.

  323. Miles :

    Date: June 20, 2015 @ 8:23 am

    I have a 2007 Honda Accord. I have charged it a couple of times and during a the day 82degrees, it’s never blows cool air but later in the evening it would it gets cold. Lately it’s just worse in the sense that, the driver side is just blowing warm air while it blows a little cooler at the passenger’s. Cabin filter is new, compressor seem to be okay when checked according to the tech, AC fans are okay except that the condenser has never been checked. Please advise because I have recharged the system exactly 3 times in 9 months.

  324. dennisb - Auto Tool Sales :

    Date: June 20, 2015 @ 3:24 pm

    Charging every time there’s a problem can cause more issues. I would chek the readings high and low and go from there. Good Luck

  325. Agustin :

    Date: July 6, 2015 @ 4:32 pm

    I have a 1996 Windstar, 3.8L, double a/c, that was cooling ok …
    A mayor leak developed on one of the hoses and the system went empty of freon …
    By mistake (what else), days later, the van was driven for an hour or so with the system a/c turned on. The compressor’s coil were burned up (smoke was visibly).
    At removing the compressor, dirt came up from it and it won’t freely turn by hand.
    What are the odds of system being contaminated if there was no freon on the system?
    I mean, after reapairing the hose and only replacing the compressor, do I will only throw my money if a complete flush is not applied ?

    Thanks for your advice …

  326. dennisb - Auto Tool Sales :

    Date: July 6, 2015 @ 5:23 pm

    Having the AC turned on doesn’t mean the compressor was on. The lower pressure switch will protect and prevent the compressor from running with a system that has low refrigerant or in your case no refrigerant. The compressor most likely was already locked up due to lack of oil in the system. Anytime a compressor locks up it is likely to have put contaminates in the system. Flushing should be done only if you are sure you can get of the solvent out before proceeding. Any left in the system can cause problems. An in line filter is the safer way to go in my opinion. Good Luck.

  327. JerryC :

    Date: July 6, 2015 @ 9:15 pm

    As a follow up to my 97 Accord issue. I replaced the expansion valve, drier and new orings at all connections. I vacuumed the system for 45 min and monitored the -25″ vac for another 45 min with no leak detected. Added approx 0.75 Oz PAG146 oil in my gauge set supply line, and required refrigerant. With an a/c temp Gauge I have had consistent 40 to 41 degree air at the vent for 2 weeks. Thanks again for your help.

  328. Dave :

    Date: August 31, 2015 @ 7:06 pm

    I have a 1998 plymouth voyager, it started leaking water inside on the drivers side floor so I took apart to see if I could tell where the leak is coming from. then I read that the hose could be clogged under the hood on the firewall behind the alternater. That ended up being the problem, I unclogged it and the water poured out. so I put the inside back together and a few days later it started blowing warm air. What could b the problem?

  329. dennisb - Auto Tool Sales :

    Date: September 1, 2015 @ 10:37 am

    I’d check the pressure readings and go from there. Could be a leak…

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