Car Heater Blows Cold – Auto Service Tips

1:52 pm DIY, How To Auto Repair


Heater hose clamps like pictured can be removed easily with special hose clamp tools.

Summary: © In this auto service repair article, we cover how car heaters work. Knowing how the automotive heater system is designed to work, allows the car owner or auto tech to diagnose problems more quickly and easily. Car heaters are designed much differently than home heaters, therefore diagnosing and repairing auto heaters requires different service procedures. Auto service tips and information provided in this car repair article is written by a master automotive technician that has many years in the field. The info. is provided in simple language that is easy to understand by anyone – experienced in auto service or not. (Be sure to read the questions and answers in the comment section at the end of the article. Also see page 2 of Car Heater Blows Cold for even more tips.)

It’s always best to have a basic understanding on how a particular system works, to be able to diagnose problems easier. When a car heater blows cold air, there are several possibilities that should be considered. Read on to learn more. Many people are unaware that there’s NOT an electric element in a car’s heater system. Heater elements are common in portable heaters used in the home – however automobiles use coolant from the car engine’s cooling system to transfer heat to the passenger compartment, through the use of a heater core. That’s why a car heater doesn’t start blowing warm air until the vehicle reaches operating temperature. The heater core looks similar to a small radiator – it has coils and fins to transfer heat to the air.  The car engine’s coolant is pumped through the heater core while the fan (also called a blower), pushes air through the heater core fins. When air blows through the heater core fins the air is warmed and in turn heats up the passenger compartment. One of the most common causes of a car heater blowing cold air is from low coolant.  As stated before, coolant is what warms the heater core – if the coolant is low, there may not be enough heat transfer from the heater core to the air to heat the passenger compartment. When it ‘s cold outside, low coolant may not cause the engine to overheat right away. If it did cause the engine’s temperature gauge to read hot, the driver would be warned and the  low coolant problem would be discovered more quickly. The point is, when checking the heater be sure the radiator is full of coolant. Once the coolant is verified to be full, feel the heater hoses that go to the firewall. With the engine at normal operating temperature, BOTH of the heater hoses should be hot to the touch. If only one is hot, this indicates there is a blockage in the heater core or there is air trapped in the heater core preventing proper flow.

Removing Trapped Air

Using a Lisle coolant funnel is the best way to remove air from a car’s cooling system. If the coolant is really brown, has been neglected, or if stop leak has been used at some time in the car’s service history, the heater core could be stopped up. The blockage can sometimes be cleared  by removing the heater hoses and using a garden hose with a sprayer to flush the heater core out. If neither of the hoses are hot to the touch, there could also be a malfunctioning heater control valve, if used on the model you’re working on. Check for presence of a heater control valve by following the heater hoses back to the engine. Sometimes, a vacuum line could have a break causing there to be no vacuum to operate the valve. Also it should be noted that if this is your first winter with this car (and you’re unfamiliar with the car’s repair history), the previous owner could have by-passed the heater core due to a leak. When a heater core leaks, the passenger side carpet will become soaked with coolant. This should not be confused with an AC (condensation) water leak. The labor involved to change a heater core is usually several hours depending on the model. This is the reason some people will loop the heater hoses together with a 5/8″ union – by-passing a leaking heater core instead of repairing it properly.

After the previous steps are taken to insure the heater core is in the loop, the coolant is full and hot water is circulating in and out of the heater core, read the following regarding the HVAC (Heating, Ventilation & Air Conditioning) case. Doors within the heater case are either controlled by electric actuators, cables or vacuum motors. Adjust the heat control to both extremes while listening for movement of the blend door. With a cable operated heater door it’s easiest to hear the door thump when it closes. If the door is not operating, find the door that controls the airflow across the heater core. If there is an electric motor that controls the door, tapping on it can sometimes make it work temporarily for testing purposes. A vacuum operated motor needs vacuum to work, so using a hand-held vacuum pump for testing is usually the easiest way to check operation. If the vacuum motor does not hold vacuum, the diaphragm is leaking requiring replacement. To go deeper into diagnosis of the AC control head’s function and diagnosis, specific vehicle repair manual diagrams may be needed.

Next Page

Related Car Repair Article and Mechanics Tools

Car Heater Blows Cold – Part 2 with more Tips

The Lisle Coolant Fill Funnel to Remove Trapped Air

Car Tools – General Automotiove Tools

Shop Heaters and Blowers – Heaters

Mechanics Specialty Tools – Cooling System Service

183 Responses
  1. Tucson Automotive Repairs :

    Date: October 12, 2009 @ 3:11 pm

    Very informative read about heating and cooling systems. We try to give our customers very straightforward information like this when answering their questions about automotive repair; it’s nice to see other people taking the same approach. Thanks for the great read!

  2. Adam :

    Date: November 18, 2009 @ 2:08 am

    I have a 97 Chrysler sebring 2.5 v6 that has a heater problem. The car only has warm or hot air after driving around for a while. Even when the temp gauge reads normal engine temperature, it still takes several min for warm air to start blowing out of the vents. Do you have any advice and thank you in advance.

  3. dennisb - Auto Tool Sales :

    Date: November 18, 2009 @ 8:01 am

    Adam, the tips mentioned in the article could help. Full coolant? Feeling the inlet and outlet hoses to make sure coolant is flowing through the core and making sure there’s no air in the system.

  4. susan Davison :

    Date: November 19, 2009 @ 12:03 am

    i have a chrysler sebring 2001. my heater blows hot except when im idling. it still blows air but cool when i put it in park and idle. Im having trouble also with my cruise control not working when i turn on my lights or use my (i think my right) turn signal when switching lanes. The weird thing is the cruise control thing is intermintent. I was surpised to get to use my lights and cruise control the other night only to have the turn signal shut it off. HELP. I just had the transmission fixed. Since then Ive heard an exhaust sound from engine. When I took the mechanic for a ride to hear it, it wasnt doing it then. sounds like I have a glass pack on it. Can you help me sort this out?

  5. dennisb - Auto Tool Sales :

    Date: November 19, 2009 @ 9:34 am

    Susan, you may have some air in the cooling system affecting the heater, this is quite common.

    Sounds like an electrical short possibly in the steering column affecting the lights and cruise. Added 12/09/2010 – Since I answered this question I’ve learned of a problem that is unique to the Sebring regarding problems with the heater when the lights are on. See my answer to Cindy which also has a 2001 Sebring – towards the bottom of this page.

    The exhaust sound may have been a dust shield interfering with the flywheel – exhaust leaks will not fix themselves, but if a shield was lightly rubbing on the flywheel, it could have worn away enough to not be touching anymore now. If it continues to make noise you may want to take it to an exhaust shop.

  6. Nicole :

    Date: November 21, 2009 @ 8:20 pm

    I have a 2002 Nissan Altima. I have the same problem as Susan with my car heater, and have had it 3 winters in a row now. My heater only blows warm air when the car is actually driving (and I typically have to be going over 40mph for the warm air to kick in), and it blows cold when I go slower than 40mph or am stopped. The first year I took it to a shop and they fixed it. They said that it was caused by a gear coming off the motor that controls the heat. I took it to another shop this year to get it fixed and they first told me it was the thermostat and put a new one in, which didn’t work. They then told me that it had to be the water pump if it wasn’t the thermostat so they put a new water pump in and said it was fixed. Almost immediately after getting it back, I realized the probelem is still there. Plus, now my air conditioner is not working either when it worked absolutely fine before taking it in to get the heat fixed! So now I have paid $250 to not only have my heat problem still not solved, but they messed up my a/c in the process and refuse to give me a refund or to take another look at it and fix it correctly at no charge. Any ideas what the real problem could be since it apparently wasn’t the thermostat or water pump? Could both the a/c and heat problem be caused by the motor again?

  7. dennisb - Auto Tool Sales :

    Date: November 21, 2009 @ 8:58 pm

    Nicole, The gear coming off for the blend door would affect the heat at ALL vehicle speeds. The reason the car is blowing warm air ONLY when your driving, could be due to the water pump pumping more water through the heater core, since the engine is turning the pump faster. Many Nissans have a problem with the radiator cap rubber seal swelling slightly preventing coolant from traveling back and forth from the coolant reservoir (plastic bottle) and the radiator. If this happens and the cooling system has a small leak (from a hose connection for instance) the system can end up with air in it, even though there is some coolant in the overflow reservoir. Particularly in Nissan vehicles if air is in the cooling system, an air-lock in the heater core can prevent the heater from working properly. See the related article (click the image below) to learn how to purge the air from the cooling system. As far as the AC, that could be a totally separate issue – checking the AC is the only way to determine what the problem is with it.

  8. DJ :

    Date: November 30, 2009 @ 7:25 pm

    I’m looking to buy a 2000 Eclipse, the person that is selling it says that the only problem is in the heating system. He says it blows hot on the left (I’m assuming the passenger side) and cold on the right (again assuming its the driver side) when the heat is on. After reading the article it sounds like it could be a plugged hose or possibly one of the doors are malfunctioning. Does this sound right to you? And if it does how involved would it be to repair the door? Thanks

  9. dennisb - Auto Tool Sales :

    Date: December 1, 2009 @ 7:35 am

    I would first check the simple things like an air lock in the system. However, it does sound like there could be a malfunctioning HVAC door or actuator. By looking at a parts breakdown of the case assembly, determine which actuator and door control the side that is not working properly *left and right are always determined when sitting in the vehicle, not standing in front of the car. After pinpointing which actuator or door assembly is at fault, the amount of labor required can be looked up in a repair manual – sometimes access is easy and other times very labor intensive (ie dash removal for access). Depending on how much trouble this is to fix, this repair could be a deal breaker.

  10. Adam :

    Date: December 5, 2009 @ 1:24 am

    Thanks for all the comments dennisb, I would like to know your comments on if a rad or heater core flush would fix my heat problem. And if so could you tell me a bit about the procedure.

  11. dennisb - auto tool sales :

    Date: December 5, 2009 @ 7:23 pm

    Adam, a plugged heater core could be the problem. Checking the temp of both hoses like I mentioned in the article above is where I would start to help determine if it is or not. If it is plugged, flushing the heater core can be done with a garden hose with a sprayer attached, be sure to bleed the air out of the system as mentioned in the above article.

  12. Domingo Roxas :

    Date: December 7, 2009 @ 3:40 am

    Car ac vents blow hot air, when it’s the cool air that is needed (tropical country). This makes inside of car too hot. What is wrong with the system?

  13. dennisb - Auto Tool Sales :

    Date: December 7, 2009 @ 7:22 am

    Domingo, you may want to check out some of our air conditioning articles, especially the one about AC gauge readings explained.

  14. George :

    Date: December 7, 2009 @ 11:20 pm

    Hey dennisb, I have a Concorde 2000 3.2l, it seems like the heater is not blowing hot air, I just replaced thermostat and filled it with coolant. Even when idle is not blowing hot air, sometimes it looks like blows warm air after a while, actuator seems working since a made self diagnose by pressing floor, mix and defrost and no errors were given. No leaking, what could be the issue???

  15. dennisb - Auto Tool Sales :

    Date: December 8, 2009 @ 7:31 am

    George, just filling the coolant is not good enough with most modern vehicles, since air can get trapped easily. Some cars even have bleeder screws, I remember the 2.7 engine in the Concorde, definitely has a bleeder screw in the top coolant housing – not sure about the 3.2 Liter. And as I mentioned before the Lisle coolant funnel does wonders to burp air out that can definitely cause an air lock in the heater core. You could have other problems with your Concorde, but you would be surprised how many times it’s just air in the system.

    A recent article that about a Dodge Durango, which had poor rear heater performance ended up having a blown head gasket which continuously introduced air from the combustion chamber into the cooling system causing a void that never could be purged. Not saying that you have a blown head gasket, but this is something that people should consider, if air keeps bubbling up when using the coolant funnel and never seems to purge completely.

  16. Jess :

    Date: December 9, 2009 @ 2:56 am

    Hey Dennisb, great article! I have a 1999 Toyota Camry CE, and recently the coolant temperature guage has been acting weird. The temperature reading drops after I turn on the car heater, and after some time less hot air starts coming out of the vents. When I stop the heater, the temperature guage goes back to normal. Also, when I am going at highway speeds and suddenly brake, the temperature guage again falls. It goes back to normal after some time. Can you please help me out on what could be the problem? Thanks!

  17. dennisb :

    Date: December 9, 2009 @ 4:23 pm

    Jess, I would first check the coolant level and make sure there’s no air in the system.

    After you’re sure there’s no air – you may also want to check the accuracy of the temperature gauge, by using a scan tool to access engine data and to make sure the temps are the same. I don’t see why stopping suddenly would change the temperature of your engine – so it could be a gauge issue or possibly wiring.

    The fact remains the engine’s temperature varying slightly shouldn’t affect the heater performance that much, there should be heat available.

  18. Jamie :

    Date: December 10, 2009 @ 1:02 pm

    I have a friend with a 2000 Saturn L series and is only blowing cold air. It doesnt get warm at all! I am trying to help because its been in the negatives and teens this week! Trying to keep friends warm!!!

  19. Dustin Ealy :

    Date: December 15, 2009 @ 1:06 am

    My girlfriend’s car isn’t blowing hot air when the heater is on. I was thinking it could be the thermostat because that is what was wrong in my car when i had the same problem. Is this possible.

  20. dennisb - Auto Tool Sales :

    Date: December 15, 2009 @ 7:25 am

    Dustin, A thermostat usually fails in one of a couple of different ways.

    1. Thermostat doesn’t open – this in addition to causing the heater not to work will also make the engine temperature over-heat.

    2. Thermostat stays open – if it stays open all the time, or opens too early (before the engine reaches the target operating temperature) the heater will not blow as warm as it should. If this is the case, usually after the car has ran awhile the vent temperature will increase gradually (at varying rates depending on the ambient temp).

    So basically, check the car’s temperature gauge to see if the engine is running at the normal operating range – if it is and at that time the heater isn’t working correctly there probably is a different cause.

  21. TRACY :

    Date: December 18, 2009 @ 2:44 pm

    Hi, I have a 1999 Nissan Altima. When my car heats up the temperature gauge does not go to the middle (in between hot and cold) as usual. It seems to only stay to the cold side which is making the heat in my car not very hot. I have heard about cars running hot before, but not running cold like my is doing. I have had the car for 2 1/2 years and this is the first time this has ever happened. I haven’t had any problems with the heat or air conditioning since buying the car. But also haven’t had any reason to maintain the heat or air and I didn’t know that there was anything in particular to do, to keep it maintained. Do you know what could be wrong? Thanks

  22. dennisb - Auto Tool Sales :

    Date: December 19, 2009 @ 9:07 am

    Tracy, regarding maintenance the coolant condition and level should be checked at every oil change. Typically the air conditioning doesn’t really need to be checked unless the performance isn’t up to par. Some cars do have a cabin air filter (yours does not) that should checked similar to the filter in your home central air system. To read more about cabin air filters and problems with low airflow, see our related repair article. The outside temperature can affect the operating temperature of your engine some. If it’s really cold outside, it could take a little longer to reach full operating temp. Based on what you’re describing, I would check the thermostat, since it may be opening too soon. The thermostat normally stays closed when the car is first started, to allow the engine time to heat up quickly to it’s optimum temperature before it allows the flow of coolant throughout the system. Also since you have a Nissan, which has a heater system, which is more prone to being affected by low coolant and air in the system – I would use the funnel mentioned previously in this car repair article.

  23. ROBERT :

    Date: December 19, 2009 @ 2:11 pm

    hi dennisb my wifes car blows only cold air,I ran the car,thermostat seems to work fine. I felt the hoses neither are hot.the car is a 98 PLYMOUTH BREEZE.what do you suggest?thank you

  24. dennisb - Auto Tool Sales :

    Date: December 19, 2009 @ 2:15 pm

    Robert, coolant flow needs to go to the heater core – there may be a heater control valve malfunctioning (if one is used on that model). I would look to see if a heater control valve is in the heater hose coming from the engine.

  25. Nathan :

    Date: December 19, 2009 @ 11:33 pm

    dennis, I have 1998 plymouth neon and just all the sudden the car is overheating and some water dripping out of the radiator cap where the car is running hot and the heat is cold the fan will still blow but the air is cold. Is this the thermostat or what?

  26. dennisb - Auto Tool Sales :

    Date: December 19, 2009 @ 11:55 pm

    Nathan, Before checking the heater, the car’s engine needs to be running at a normal temperature. Yes, it could be a thermostat, a cooling fan or any other number of causes. After the overheating problem is diagnosed, the heater most likely will work.

  27. IVAN :

    Date: December 20, 2009 @ 9:27 pm

    Hi Dennis B.
    I have a pontiac Trans sport 1996. I had so many opinions regarding the heater system since it stopped working. There is no hot air coming in the car making it impossible to drive in snow. I changed the blower motor, thermostat, filled with coolant and it would not work. How could i check the heater core, how can i locate the heater core in my car and know if it is working?
    The low coolant light is on in my panel, but the car is filled with coolant. maybe that might be a clue.
    Please help me out.

  28. dennisb - Auto Tool Sales :

    Date: December 20, 2009 @ 9:39 pm

    Ivan, Your 1996 Pontiac Transport most likely has a 3.4 V-6 with at least one bleeder screw in the coolant pipe (if I remember correctly). First off I would check to make sure all the air is out of the cooling system using a Lisle coolant funnel and bleeding the air out with the bleeder screws. This along with the other tips I’ve included in the article should help to pinpoint the problem.

    Low coolant light – if the coolant is at the correct level in the reserve bottle and the radiator, the switch is probably stuck or defective. The coolant level switch in your vehicle is most likely just below the radiator fill cap in the radiator (in some vehicles, it is in the plastic reserve bottle/coolant reservoir). In either case that would not prevent the heater from working as long as the coolant level is actually full.

  29. Dee, Belfast, N.Ireland :

    Date: December 22, 2009 @ 5:59 pm

    Hi dennisb,
    Great site with informative & prompt advice, great work!!!

    I’m hoping you can help me out a little here: with snow and -3° here in Belfast, Northern Ireland, I need my Renault Laguna’s heater to be working, but I’ve been having problems over the past days:

    The car has been blowing cold air when idle although warm when I’m driving. In order, I’ve checked the coolant level which is fine. With the car just started I then felt the inlet and outlet hoses (under the hood) going into the Heater Core/Matrix to establish if the inlet-hose got warm first then the outlet shortly after. The inlet hose did get hot in a short while, but the outlet hose took a few MINUTES later to heat up and wasn’t as warm as the inlet hose, thus indicating it could be an air-lock or blockage.

    As mentioned on other sites I then drove the front of my car up onto the small metal ramps – to ensure the coolant tank/reservoir is at the highest point, then with the cap off I started the car and let it run idle for a few minutes while giving it a few gentle revs – in order to let any trapped air in the system to escape. Some gurgles/bubbles did come via the coolant tank (with cap off) although I still run it a little longer while keeping a close eye on the coolant level (ensuring their was enough inside…). However, the problem persisted.

    Carefully using a screw-driver to prise open the safety-clip, I then removed the two hoses, inlet & outlet (joined together at the ends) going into the heater core/matrix, behind the dash but under the hood. This revealed the two holes leading into the heater matrix, still under the hood, (no work inside the car!).

    I then pressed a garden hose-nozzle into the outlet hole in order to BACK-FLUSH the matrix, which is safe to do. Some liquid-crud and dirty coolant came out through the inlet hole as expected. I did this until the water came out clear through the other hole. I then re-connected the two hoses to the matrix-holes under the hood, ensuring the clip/s were intact again.

    The problem still persisted, albeit there were times I thought it was sorted due to some luke-warm air coming through the vents for a few seconds, but then cold again.

    I then replaced the thermostat with a new and original one, but still the problem persists.

    I’m wondering if there’s still more trapped air in the system, or if a vent may be stuck or something, as I’ve heard the odd gurgle behind the dash sometimes when driving and, warm air comesout the vents only when I’ve been driving at least a mile or two, but goes cold again when I slow or stop.

    Note: I’ve tried to clearly detail what I’ve done so far to give you a better picture, and in case the actions help someone else…

    Maybe you can give me a pointer mate?

    Many Thanks!

  30. Dee, Belfast, N.Ireland :

    Date: December 22, 2009 @ 6:04 pm

    Ps. My two hoses going into the heater matrix resemble those as shown in the picture at the top of the above topics, albeit mine are joined like a double-barrel shotgun at the end. Cheers!

  31. dennisb - Auto Tool Sales :

    Date: December 22, 2009 @ 10:13 pm

    Dee, it’s possible even though you were able to back flush the heater core that it still may be restricted. For the heater core to work properly there needs to be a unrestricted flow to allow enough heat exchange. When the garden hose is hooked up and water being ran into it – the flow of water coming out of the heater core should just as much as comes out of the hose – unrestricted. Reduced flow will cause the heater not to work sufficiently.

  32. Dee, Belfast, N.Ireland :

    Date: December 24, 2009 @ 7:08 am

    I think you’re right bud. When I insert the hose to one hole (outlet) the water flows out the other (inlet) with a good flow. However, when I flush through the inlet the water trickles out the oulet hole – possibly indicating a restriction.

    I’ve now fully bled the system with not a single bit of air trapped inside, therefore it has to be a blockage in the matrix. I’ve read about carefully inserting diluted Hydrochloric Acid into the matrix for about 5 mins, before giving it a good flushing out. The acid is meant to really help in breaking up any gunk etc inside.

    Providing it’s nothing Alkali or caustic based going inside the matrix which can badly affect aluminium (which of course the matrix and radiator is made up of.

    Thanks again pal and I hope you and yours have a very Merry Christmas!!


  33. dennisb - Auto Tool Sales :

    Date: December 24, 2009 @ 11:26 am

    Thanks Dee. BTW 70° at the moment here in Florida :) Merry Christmas!

  34. damar :

    Date: December 25, 2009 @ 4:44 am

    Hey dennisb I have 1998 acura rl 3.5
    I replaced my thermostat but my coolant is brownish will that effect the heat coming into my car because its not as hot as it should be. Also sometimes when im driving the blower starts to blow cooler I located the bleeder screw and there seems to be no air in the system helppppp me please.

  35. Dee, Belfast, N.Ireland :

    Date: December 25, 2009 @ 7:25 am

    Aaaa, it’s Florida you’re based in!
    I’ve been with the family the last two years – staying at my father-in-law’s villa (Blossom Hill Loop, off the 127 & 192, near the Wal-Mart and Lowes DIY.

    We love Florida. I was even offered a job there with my company and was so close to taking it. It just didn’t pay well enough though and so couldn’t afford to go (while supporting my family back here in Belfast for a while).

    Maybe another day.

    Should be going for another 2 or 3 week vacation again though in 2010. Looking forward to it!!!

    I’m envious!! :-)

  36. STROW :

    Date: December 30, 2009 @ 9:14 pm

    Hi Dennisb
    I have toyota camry 1997. The heater works well while it is in parking or riding in less than 25mph. If i drive above 30mph I stop feeling any heat coming from the heater. It is also related with the temp gauge.The gauge indicates operating temperature (almost in the middle of cold and hot) while the car is in parking or idle. It drops to cold while i am driving above 50mph and then the car starts freezing. The air blowing from the heater gets cold. I have checked the coolant and it is on the right level. Can you please tell me what the problem might be?

  37. Chris :

    Date: January 9, 2010 @ 10:14 am

    Hi Dennisb, I have a 2001 Ford F150 Supercrew. My heater will blow warm air for about 20 seconds then gets progressively cooler. I recently had the radiator system flushed and when I check, both sides of the heater hoses are hot…when I switch the heater on I can hear a faint clicking around the heater core behind the glove box. All fuses are good too. Any advice…?Freezing in Florida @ 20 degreees.


  38. dennisb - Auto Tool Sales :

    Date: January 9, 2010 @ 12:12 pm

    Chris, It’s possible there is a problem with the heater blend door or actuator. The blend door in that model has been known to break. First though I would check to make sure it’s not just a plugged heater core – it can still feel warm on both inlet and outlet but not have enough flow. Since you say it does blow warm for a few seconds, that indicates that the air-flow may be correct, maybe just not enough water-flow through the heater core. I would try spraying water through the core with both hoses off to make sure there is PLENTY of flow (not just a tiny stream).

  39. marty :

    Date: January 9, 2010 @ 8:01 pm

    hey Dennis my wifes toyota 2004 camry’s heater will run you out if its moving but as soon as you stop it blows cold air fluid is good both hoses are hot ect..
    any tips ?

  40. dennisb - Auto Tool Sales :

    Date: January 9, 2010 @ 8:31 pm

    Marty, nothing comes to mind except the usual – low coolant or air in the system.

  41. STROW :

    Date: January 10, 2010 @ 4:52 pm

    Hi Dennisb
    I have toyota camry 1997. The heater works well while it is in parking or riding in less than 25mph. If i drive above 30mph I stop feeling any heat coming from the heater. It is also related with the temp gauge.The gauge indicates operating temperature (almost in the middle of cold and hot) while the car is in parking or idle. It drops to cold while i am driving above 50mph and then the car starts freezing. The air blowing from the heater gets cold. I have checked the coolant and it is on the right level. Can you please tell me what the problem might be?

  42. yonathan :

    Date: January 10, 2010 @ 9:00 pm


    I have same problem as strow. my 97 toyota camry’s heat works good on idle, and gets cooler when i drive (only in cold weather.) my engine must be extremely well cooled, cuz it will warm up idling, then i take off and watch the temp gauge go down! Thermostat has been changed but didn’t help. Coolant is full on the reservoir too. Please any tips ?

  43. yonathan :

    Date: January 10, 2010 @ 9:02 pm

    ………….coolant is to the level “full” on reservoir actually.

  44. Garth :

    Date: January 11, 2010 @ 3:22 am

    Hey Dennis,

    I have a peugeot 307 TDi 2003, and in 45 deg C Australian heat, air conditioning is a must.

    The problem is when turned on, the AC only blows cold air from one of the central vents, while all the other vents blow hot air. I have tried all the different settings and can’t seem to fix this. Any ideas? Cheers

  45. dennisb :

    Date: January 11, 2010 @ 11:38 am

    As far as the Toyota only heating well at slow speeds or idle, there could be a problem with the thermostat staying open. Sounds like the coolant is continually circulating and never allowed to heat up until the car stops and has less airflow across the radiator and also the pump is turning less revolutions. The t-stat should help to maintain normal operating temperature – and warm enough coolant to operate the heater.

    If the heat only works while going at higher speeds I would suspect a partially restricted heater core (or low coolant).

  46. dennisb :

    Date: January 11, 2010 @ 11:43 am


    Wish you could send some of that heat to the states (45C = 113F).

    My guess would be that there is an issue with one of the actuators (controlled by vacuum or voltage) which operates a door. I’m not familiar with your model, but that is where I would be looking.

  47. josh b :

    Date: January 13, 2010 @ 6:44 pm

    I need some help. i have a 2005 chrysler pacifica 3.5L, AWD, last night my heater in the car stopped working. the front doesnt blow out any air at all and the back only blows out cold air. i checked the fuses, relays and it has plenty of coolant. Any suggestions??

  48. dennisb - Auto Tool Sales :

    Date: January 13, 2010 @ 9:36 pm

    Josh, two different problems more than likely. NO AIR blowing at all in the front could be a front blower motor or poor connection to it. The front blower motor is located under the dash on the passenger side behind the glove box.

    The rear problem could be a door actuator or plugged heater core. Checking a repair manual to understand how the rear system is comprised would be necessary for me to make a better guess.

    I hope it warms up soon!

  49. lou norris :

    Date: January 14, 2010 @ 12:16 pm

    Will removing the thermostat from my 1999 dodge caravan 3.3 auto, cause the heater not to work? When van is sitting for a little while idling and the temp. go’s up a little bit then the heater will blow warm air, but when you start driving down the road and temp. drops to normal it blows cool air.. whats up with that??

  50. dennisb - Auto Tool Sales :

    Date: January 14, 2010 @ 12:24 pm

    Lou, yes removing the thermostat can affect the heater performance. It can also cause other problems like a fault code for the engine not reaching operating temp. fast enough.

  51. Gilbert M :

    Date: January 14, 2010 @ 3:26 pm

    Dennis, I have a ’96 Suburban that I think has low heater air temp. The maximum it puts out is 100F on low fan speed. At higher fan speeds the output temp drops to 80F. What should I expect for a normal air temp output?

  52. dennisb :

    Date: January 14, 2010 @ 7:31 pm

    Gilbert, the maximum vent temperature should maintain around 100 degrees on max (recirculate) setting. The heater air temp should be checked after the the engine reaches normal operating temperature. Ambient/outside temperature can affect the car’s heater performance.

    My car right now with 72 degress outside temperature has a maximum vent temp of 110 degrees with little change on different blower speeds.

    On max setting, eighty degrees seems too low no matter what the outside temperature is. Any number of things could cause under par performance. One of the most common causes (besides low coolant) can be a slightly restricted heater core – that’s where I would be looking after ruling out easiest things first.

  53. joe cartee :

    Date: January 30, 2010 @ 8:29 pm

    My son has a 1998 F150, We replaced the radiator because of a leak. We have no heat. Both hoses at the heater core are cold. We removed the top hose at the thermostat and the water continues to flow. Maybe the thermostat is stuck open ?

  54. Sam :

    Date: February 1, 2010 @ 6:59 pm

    I have a 92 acura legend. I have problem of getting heat when engine is cold. I have to drive like 5 min before heat would suddenly would come on. Then one cold morning, I had the engine blowing coolant into the reservoir and spitting antifreeze out with engine temp way up high. I decided to change my thermostate and radiator cap and bleed air from the system via bleeding valve and the car was working fine for about two months with heat coming on nicely although I seemed to smell some sweet smell of coolant from the heater when I start the car and the smell would quickly goes away. As the time goes by, it seemed like my heater getting worst of each day and suddenly I have a repeat of what happened two months ago with my heater not coming on until 5 min later and then my engine is blowing hot air into my reservoir and temp way up high. I wonder why all this air built up in the cooling system and what is the root problem?

  55. dennisb - Auto Tool Sales :

    Date: February 2, 2010 @ 7:20 am

    Sam, I would pressure test the the coolings ystem and do a carbon test to see if there is exhaust in the cooling system.

    1. A coolant leak in the engine’s cooling system could allow coolant out and air in.

    2. Exhaust in the cooling system (carbon test to determine) could mean a leaking head gasket which would cause air (exhaust) into the cooling system.

    Either scenario could be the problem with repeated cases of an air-lock in the cooling system.

  56. Dan :

    Date: February 2, 2010 @ 12:46 pm

    my car is a ford fiesta zetec 1999 and the for past two days the heater has been blowing cold air. i have checked my collant all hoses are warm and the engine is running at correct temperature. what could be the problem ?

  57. Mike :

    Date: February 4, 2010 @ 11:04 pm

    2002 Pontiac Montana blows hot air then cold air. Eventually it starts blowing hot again. What would cause this to happen?

  58. Rena :

    Date: February 8, 2010 @ 7:19 pm

    I have a 2003 Hyundai Santa Fe v6 (3L). The heat works at first but after using the heat for 45-60 min’s it starts blowing cooler. Any ideas on what to look for or where to start would be appreciated. Thanks!

  59. Adam :

    Date: February 14, 2010 @ 5:12 pm

    I have a 2003 chevy s10, the heat is giving me some problems. I changed the thermostat and drained and replaced coolent. It takes a really long time to get any warm air out of it and then turns cold once I start driving. Any ideas would be helpful. Thanks

  60. Matt :

    Date: February 16, 2010 @ 5:05 pm

    I have a 99′ ford Mustang, and when I turn the heater on, it will blow out warm air at first but then turn ice cold. I replaced the thermostat and filled the coolant, but it did not fix the problem. I am hoping that the heater core does not need replaced. Just wondering if you had any idea’s on what it could be.

  61. Leah :

    Date: February 17, 2010 @ 10:16 pm

    I have a 2001 Toyota Camry and a few months ago the air stopped blowing out of the vent on the 2 lowest settings, but would work only when the gas pedal was pushed. Eventually that stopped working. Now air only blows out when it is on the highest setting, heat or a/c. What is the problem? How much to fix it?? Thanks!

  62. Alicia :

    Date: February 18, 2010 @ 2:14 am

    I have a 93 Dodge Grand Caravan and I had to actually test a theory on it before I could start asking around about the problem. When I use the heat it seems to barely work. I went out to the store late in the evening and realized that as I hit 30mph the heat kicked on real strong but as soon as I would go below 30mph the heat turned to cool air, as if I had just switched on the AC. What could this problem be and how much would it cost to fix this?? Thank you in advance!

  63. Jackie :

    Date: March 4, 2010 @ 6:09 pm

    How much should I be charged to replace the heater core in my 2005 Sebring and does the dash board need to come off to do so?

  64. jason :

    Date: March 7, 2010 @ 8:38 pm

    I have a 1993 geo storm the heat works when i sit and leave it running but once i start driving it the temp gauge goes all the way down and blows cold air

  65. Ron :

    Date: March 18, 2010 @ 8:25 am

    I have a 96 chrysler concord it will start blowing cold air then overheat. I have replaced water pump radiator and several thermostats. Any idea why this keeps happening ?

  66. dennisb - Auto Tool Sales :

    Date: March 18, 2010 @ 8:36 am

    Ron I would check for a blown head gasket, If the head gasket is leaking exhaust into the cooling system, it could cause the problem you are describing.

  67. jessica :

    Date: October 4, 2010 @ 9:40 pm

    Hi there maybe you can help. I have a 95 ford thunderbird lx and the heater blows only cold air. The ac works fine although it does start to run hot when you turn it on to high. When I bought the car the heater was disconnected and the mechanic there hooked it back up it looked like it was hooked to a t-hose or something. The low coolant light does come on once in awhile, I hope this helps you help me.

  68. dennisb - Auto Tool Sales :

    Date: October 5, 2010 @ 6:39 am

    Jessica, the first sign that there is a problem with the heater core is that the previous owner has had it by-passed. Like mentioned in the article, if a heater core leaks and the owner decides not to replace it (because of the expense or trouble) the heater core can be bypassed. This is the T-hose you are referring to. It could be partially plugged or have a leak – or BOTH. This would explain why it was out of the loop and why your low coolant light comes on now. The mechanic can pressure test the cooling system using a coolant pressure tester.

    In some cars if the heater core leaks, the coolant will drain out the AC evaporator drain hose underneath the car instead of soaking the carpet on the passenger side. This may be why you don’t mention any coolant on the floorboard, although you may smell the coolant – a sweet/sour sickening smell usually in the passenger compartment. On your car the dash would need to be removed to access the heater core for replacement. Due to the age of the car, the expense if you have to pay a shop may not be justified, although that is up to you. Good Luck.

  69. David :

    Date: October 16, 2010 @ 11:51 pm

    I have a 2002 Chevy Silverado-1500 series, V8. This summer both the a/c and the heater went out the same week. Never smelled anything, nor did anything drip. The coolant level is full, and both the inlet and outlet heater hoses are hot to the touch. Does that mean my heater core is bad? The fans blow fine, but it’s always cold air. I really appreciate you taking time out of your busy schedule to respond to all of us:)

  70. David :

    Date: October 17, 2010 @ 12:09 am

    Could it possibly be the HVAC Control Module?

  71. David :

    Date: October 17, 2010 @ 1:37 am

    I FINALLY FIXED IT! After a few months of no a/c or heater, I finally figured it out. It was simple as simple gets. A pigtail had become disconnected under the dash, probably from when my daughter sits in the middle with her feet dangling nearby, or from my wife and the vacuum hose. Regardless, your step by step diagnosis above really helped in telling me what “wasn’t” the problem. Very thorough self-diagnosis. Again, thanks!

  72. dennisb - Auto Tool Sales :

    Date: October 17, 2010 @ 7:01 am

    David, glad you were able to figure the problem out. Sometimes it’s the simple things that can be brain racking.

  73. Sarah :

    Date: October 17, 2010 @ 5:16 pm

    If the car does have a blockage like described in your very helpful article – is the car safe to drive? My mechanic friend is coming to look at the car in 3 days and I wonder if I could do more damage if I am still driving it? My journey to work is 4 miles each way so a very short journey?


  74. dennisb - Auto Tool Sales :

    Date: October 17, 2010 @ 9:04 pm

    Sarah, no. A restriction in the heater core would only affect the comfort level in the passenger compartment and would not directly cause a problem with the engine overheating.

  75. Dave Fisher :

    Date: October 18, 2010 @ 6:18 pm

    Thanks for this great article, I am wondering if you would know what would cause warm air coming out of the front air ducts but cool air out of the defroster, this is when I have the heat on.

  76. dennisb - Auto Tool Sales :

    Date: October 18, 2010 @ 7:15 pm

    Dave, usually the HVAC doors don’t seal off air completely; so it’s common to have a little air coming out vents that are NOT selected. The part that does not make sense is that you say it is different temperatures. This may be one for tech to diagnose in person. Good Luck

  77. Dave Fisher :

    Date: October 22, 2010 @ 2:01 pm

    Thanks for your comments, I too find it strange as the heater doesn’t blow out hot, but warm enough for the bottom and center when selected, the only time the temp gets cool (while in heat mode) is when I put it on defrost.

  78. Estella :

    Date: October 28, 2010 @ 10:10 am

    I am having trouble with 2001 Dodge Intripid. The heater get warm when I drive a distance. / Are they easy to change?

  79. dennisb - Auto Tool Sales :

    Date: October 28, 2010 @ 10:26 am

    I would check the things mentioned in the article. If you are asking about changing the heater core, no it’s not an easy one – the Dodge Intrepid requires dash removal to access the heater core for replacement.

  80. Leeanna :

    Date: October 29, 2010 @ 1:18 am

    I have a 1999 Ford Taurus. Im having a problem it takes about 45 min just for the temp gauge to barely move off of the C mark. And when I turn on the heater it blows warm for roughly 3-4 seconds. Ive replaced the thermostst filled it with fluid also had the heating coils changed twice in the last year, For somereason noone seem to know what the problem is can ya help me?

    Thank you for your time,
    Freezing in Oklahoma.

  81. dennisb :

    Date: October 29, 2010 @ 9:22 am

    Leeanna, first off I would check the accuracy of the gauge. It shouldn’t take that long for the engine to reach operating temperature (even if the thermostat was stuck open). A scan tool can be used to check the data screen to see if the temp reading coincides with the gauge in the dash.
    Second, if a repair shop has replaced the heater core twice in the last year I would suspect a very dirty cooling system causing the core to get restricted quickly (clogged up). Have the repair shop explain what has caused the heater core to need replacing after such a short time. Some systems may require a new radiator and a thorough flushing to clean the system out enough to prevent the heater core from getting plugged up again quickly. This is particularly common when someone has added stop leak in the cooling system. The warm air for 3-4 seconds also leads me to think there’s restricted flow due to contamination like rust or stop leak. Good Luck.

  82. Mike T :

    Date: November 1, 2010 @ 9:23 am

    I have a 2008 Chrysler Sebring. The defrost always blows cold air even when the blower selecton button is on blower / floor the defrost always blows. Sometimes however if you place the selector on blower and start the vehicle you can hear it switching from defrost to blower and then it will blow hot air and function normally. The heat seems to work about 20% of the time only overall.

  83. Jakem777 :

    Date: November 1, 2010 @ 10:54 am

    My 2001 Chrysler Sebring temp gauge keeps flucuating and some times hits HOT and the heat isn’t blowing hot. I had it flushed and a new thermostat put in… I don’t know what to do now!!! :(

  84. Mike :

    Date: November 5, 2010 @ 6:27 am

    Hi, i have a 2003 Audi A4 1.8T, the coolant light came on and so i filled it with the 50/50 coolant, and now it blows very cold air, when it was on low it was hot now its full and its cold! please help

  85. Greg :

    Date: November 6, 2010 @ 2:46 pm

    I have a 2002 Dodge Stratus that is acting screwy. The heat comes on once I go above around 35mph but at a stop it will go cold. Also, the temp gauge rises and the fan kicks on when I go through a drive-thru. When I’m driving the engine temp is fine.

  86. Jessica :

    Date: November 6, 2010 @ 4:37 pm

    I have a 03 Neon and the heater has been blowing cool air. Last year the heat worked great. So far the thermostat has been replaced and the blend door has been checked. Both are fine. The coolant level is fine also, though it is a little dirty. What else should we check? Thanks.

  87. Dee :

    Date: November 9, 2010 @ 8:52 am

    Dennis, I have a 1993 Nissan Maxima GXE. I just had the coolant replaced. When I turn on the heater, it blows warm on the driver’s side but cool on the passenger side. Also, I notice that cool air seems to come in through the vents even when the controls are turned off. Any suggestions? Thanks!

  88. dennisb - Auto Tool Sales :

    Date: November 9, 2010 @ 9:33 am

    Dee, if the coolant level is low at some point or like in your situation, the coolant was changed – air pockets can be trapped in the system. This seems especially true when it comes to Nissans. Using the Lisle coolant funnel to fill the system is one method to help burp the air out of the heater system. See the related article for more information on this (click the image below).

    If there’s still a problem after the air is bled out of the cooling system, then there could be a door or actuator problem, but first eliminate the air lock problem.

    Regarding the air entering even with controls turned off – The system is NOT completely air tight (it is normal). This seems to be noticed more when it is COLD outside.

  89. bryan s :

    Date: November 11, 2010 @ 7:40 pm

    hello i have a 2002 chevy malibu that i just replaced the upper and lower intake gaskets on. now it seems to blow cold at idle and leaks out of the overflow on the resivour tank . any ideas im at a loss.

  90. dennisb - Auto Tool Sales :

    Date: November 11, 2010 @ 7:46 pm

    Bryan, sounds like air in the system. I would use the Lisle coolant funnel as mentioned before. Some of the 3.4 Chevys also have bleed valves to help get the air out. If air locked in the system isn’t the problem I would suspect the thermostat. Good Luck

  91. bryan s :

    Date: November 11, 2010 @ 8:17 pm

    thank you dennis. do you think there may be a possible head gasket issue? also where can i buy that funnel? thank you

  92. B.T :

    Date: November 13, 2010 @ 11:20 am

    hey i have a 2000 celica gt-s that’s blowing only cold/warm air. I’m trying to locate the blend-air door and can’t find anything online.

  93. dennisb - Auto Tool Sales :

    Date: November 13, 2010 @ 10:22 am

    Bryan, you can read more about the funnel below – also the link going directly to the product for sale too.

    Related Article and Specialty Tool
    Lisle Coolant Funnel for sale

    How to Use the funnel with YouTube Video

  94. Chelsea :

    Date: November 19, 2010 @ 9:09 am

    Hi Dennis, I have a 2005 Chrysler Pacifica that will only send heat through the upper air vents, instead of the floor vents. On the control panel it says that it is blowing through the floor vents. When I change settings (floor, upper, defroster, defroster and lower) it has no effect, the hot air still only blows through the upper vents. Any suggestions you have would be greatly appreciated. Thanks!

  95. dennisb - Auto Tool Sales :

    Date: November 20, 2010 @ 10:39 am

    Chelsea, On cars that use vacuum to control the doors in the dash – I would say the most likely cause of the mode defaulting to the defrost vents is a vacuum leak.

    The Chrysler Pacifica does NOT use vacuum to control the HVAC (Heating and Ventilation & Air Conditioning). It uses low voltage electric actuators to change the modes, overseen by the A/C Heat control head.

    Here’s something that may help with Pacificas when the mode is stuck in any one position like you have described:

    Pacifica HVAC Reset Procedure – Calibrate Steps
    Try running the calibration test. Hold the POWER button and the RECIRCULATE button down at the same time for about 5 seconds. The control head will start flashing to indicate the test has been activated. The self test should be done in about 20 seconds. If the control head continues to flash, this means there’s a fault code stored in the Automatic Temperature Control (ATC) system. An automotive scan tool will be needed to access codes from the ATC system. Good Luck.

  96. chunky-jeff :

    Date: November 20, 2010 @ 2:42 pm

    Dennis, thanks in advance for your opinion.
    96 grand am, I blew the front head gasket and replaced it then added a stop leak for small leak on back head gasket. Now water is shooting out of the radiator cap ONLY when it reaches driving temp. This is when I overheat. Now replaced the radiator, water pump and thermostat. There are no leaks anywhere. Where could the blockage be, I’m thinking in the heater core?

    The mechanic doing the work writes the question like this …..

    Why does water spew from surge cap when car gets up to temp and the heat in the car blows cold but when I open bleeder for a second or 2 then close it we get heat for a minute or 2 and the fluid stops spewing from surge cap. Then the procces keeps repeating, theres no way I still have air in system or is the heater core clogged. Is it possible theres ports clogged in the heads? There is no fluid leaking from outside motor anywhere except the surge tank cap..

  97. dennisb - Auto Tool Sales :

    Date: November 20, 2010 @ 6:08 pm

    chunky-jeff, first – it’s not normal for stop leak to be used, especially to stop a leak from a new head gasket. Stop leak could restrict the flow of coolant in the heater core, radiator and ports in the head.

    What I would be asking myself if I was working on this car is “what caused the head gasket to fail originally?” Or was it even bad to begin with since the overheat problem is still present.

    It sounds like it could be a faulty impeller on the water pump. To check for water pump flow have the mechanic do the following.

    Measure three temperature readings from the car with an infrared thermometer.

    1. Radiator temperature.

    2. Engine block.

    3. The vent temp with the heater on maximum.

    The three temperature readings could indicate that the water is not flowing properly. A cold vent temp with a “warm” engine and a cool reading at the radiator is the main indicator.

    A more direct way to check flow from the water pump is to remove the upper radiator hose from the radiator. Have someone start the engine for a few seconds to see if there is water pumping out.

    The impeller on the water pump could come loose or can deteriorate from rust or electrolysis due to lack of maintenance or proper ground straps.

  98. Tony :

    Date: November 20, 2010 @ 7:43 pm

    Hay Dennisb I have a 2004 Chrysler Pacifica 3.5 last winter about half way trough winter heater stopped working in the front no air came out of the front at all only cold air came out from the back vents around June my car was in a flood it only got Carpet wet so it was not to bad I let my car dry out for a day and so when I went to go drive it I turned on the ac just to see if it worked and it did it was like nothing never happened the heat worked fine from front to back and also with the ac ok here is where it gets crazzy I went to start my heater today And it started doing the same thing all over does not blow anything from front only from the back but the back blows cold air and even if the car is heated up it still blows cold air from the back and nothing from the front PLEASE PLEASE help I live in Wisconsin and it is so cold we only have one vehicle and it’s COLD. Thanks mr Dennisb

  99. dennisb - Auto Tool Sales :

    Date: November 20, 2010 @ 8:19 pm

    Tony, sounds like a bad connection or faulty blower motor for the front not any blowing air. This will require using a tester like a multi meter or power probe to help pinpoint the loss of power. Sometimes you can tap on the blower motor and make it work temporarily. If this is the case the blower motor will likely need to be replaced. Not much of a surprise especially since the car has been in a flood.

    As far as the rear heater, it will take some diagnostic steps to determine the problem. Good Luck.

  100. dennisb - Auto Tool Sales :

    Date: November 21, 2010 @ 7:28 am

    “Funny smell” is the uncle that sent his pregnant niece on her way with a leaking cooling system! Just Kidding.

    Jillian, could be a hose, freeze plug, water pump etc. Have it pressure checked and repaired. After the system has been repaired and there are no coolant leaks the heater should work again. Like explained in the car repair article above, the heater uses coolant to heat the heater core, so if there’s no coolant or the system is low it cannot work as designed.

  101. Jillian :

    Date: November 21, 2010 @ 7:07 am


    I have a 1999 Ford Taurus. 2 nights ago, my car had a really funny smell, I thought with my pregnant nose I was just smelling things. Then I drove home from work, the smell returned, and steam was coming from under my hood. After popping my hood, I could see my really dirty anti-freeze spraying everywhere. My uncle informed me it is probably just a hose. Could this be something else? Also about halfway home from work, my heater went from blowing perfectly to blowing cold. Would this most likely be because the anti-freeze was now all over my car rather than going through the hoses to the heating core, raidiator, etc? What else could have caused the instant change?

    Thank you

  102. Chelsea :

    Date: November 21, 2010 @ 10:33 am

    Thanks Dennis for your help. I went through the reset procedure, the control didn’t continue to flash but the car is still only blowing out of the upper vents. I will go ahead and have someone check the codes, just in case. If you have any other suggestions that would be great! Thanks again!

  103. Bill :

    Date: November 22, 2010 @ 10:02 am

    I have a 93 Buick Park Avenue. The temperature gauge in warmer or hotter weather runs at normal while on the freeway but then will heat up to 210 when stopped at a light. Now with the cold weather in the morning, 20 to 40 degrees) the temperature gauge heats up about 180 on the gauge (20 degree increments on the reading.) Then after the stat opens in goes down to 140 while driving on highway. Then when stopped for a few minutes will go up to 180. The heater is blowing hot air when warmed up and the car is running good. I can’t figure out why this gauge is bouncing around from 195 when warm outside to 210 when stopped and running at 140 now that it is cold? I cahnged the stat last summer and the coolant. Coolant level is fine. I wonder if the temperature gauge is just bad?

  104. dennisb - Auto Tool Sales :

    Date: November 22, 2010 @ 10:19 am


    140 degrees seems way too low. I would look at scan tool data to be able to see and compare temperature readings. It could be that the temperature sending unit or the gauge is inaccurate.

  105. steven :

    Date: November 23, 2010 @ 8:40 pm

    my 1997 ford f150 heater doesn’t blow hot air, for a month all it did was blow hot no matter what setting you turn it it still blows hot , now its the other way around all it blows now is cold. the back of the knob is not cracked either.

  106. dennisb - Auto Tool Sales :

    Date: November 24, 2010 @ 10:40 am

    Steven, sounds like a control issue – either with the head or actautor.

  107. Rob :

    Date: November 27, 2010 @ 6:41 pm

    I have a 01 Dodge Caravan, it has a lot of cold air coming out from the passenger side floor, everywhere else it blows hot air. The cold air is not coming out of the actual vent but from an rectanglar opening next to the blower motor.



  108. dennisb - Auto Tool Sales :

    Date: November 27, 2010 @ 7:26 pm

    Sounds like the cabin air filter cover fell. I would look for any extra pieces floating around, maybe underneath the passenger seat.

  109. Heidi :

    Date: November 28, 2010 @ 10:35 am

    I own a 97 Pontiac Bonneville, my hoses get hot but it blows cold air into the car. I had my thermostat replaced plus the coolant and all that is full. what do you think the problem could be I was told the doors might be froze shut.

  110. dennisb - Auto Tool Sales :

    Date: November 28, 2010 @ 2:49 pm

    Heidi, sounds like either a restricted heater core or something to do with the doors, actuators or control head. It’s gonna take some hands on time to diagnose the problem.

  111. spsyed :

    Date: November 28, 2010 @ 3:22 pm

    Have a heating problem with my 1998 Renault Laguna. My local garage claims that it has changed the heater-matrix, water pump and thermostat, costing me £350 parts and labour so far this winter (2010). The engine-radiator never over-heats. There is no water leak. There is no oil leak.

    The car has heat up at idle speed as the car temperature meter goes up from cold to normal mid-way. The heat fades away gradually when the car is being driven over 30mph cruising speed as the temperature meter goes from normal mid-way down to cold level. There is heat at motorway speed.

    Without seeing the car, another garage now claims that the car may need a new pollen filter to cure the heat problem. Is that right? If not, what else would cause the problem?

  112. dennisb - Auto Tool Sales :

    Date: November 28, 2010 @ 5:24 pm

    Sounds like the thermostat could be staying open too long. I don’t see how a pollen (cabin) air filter would affect the cars operating temperature. Good Luck.

  113. John :

    Date: November 28, 2010 @ 6:50 pm

    Dennis, I bought a 96 Chrysler Sebring with 160K miles from a friend seven months ago for $2K but found out last month that the heater isn’t working, neither is the A/C. I took it in to Sears and they gave me a quote of $900 because of the time it would take to get to the heater core-they almost didn’t want to touch it because of access would mean going through airbags area(liability). I told them it’s not worth it and figure I’ll survive the winter using the heat from the engine since I get a small amount every few minutes. My question is, is this going to be enough for the windshield defogger this winter?

  114. dennisb - Auto Tool Sales :

    Date: November 28, 2010 @ 8:06 pm

    John, I’ll reserve comment about “with friends like that who needs enemies?” I recommend getting the heat and AC fixed since they both work together. The AC removes moisture from the passenger compartment and heater warms the windshield to help defrost it. Many cars cycle the AC compressor on in defrost mode and the driver never realizes it. One will not work as well without the other to defog the windshield. I’m not sure what you mean when you say “heat from the engine since I get a small amount every few minutes“. The heater core does get it’s heat from the engine by way of the coolant (as the article covers). Sounds like you may have a partially blocked heater core if you are getting some heat. In the article we talk about trying to flush it with a garden hose. This doesn’t always work, but it is definitely worth a try. As far as the shop that didn’t want to touch it because of liability – this tells me they are not comfortable doing dash work. Nothing wrong with that but they should admit it. You are better off not letting them touch it if they are not confident in doing the work. There are plenty of shops that remove dashes all they time without a second thought about deploying an airbag. John prepare for a cold winter! Good Luck.

  115. John :

    Date: December 1, 2010 @ 1:12 am

    Thanks Dennis, I would never have known the AC works in conjunction with the heater to defog the windshield. I’ll look into having it flushed. At least now I have some hope of keeping warm this winter.

  116. Mari :

    Date: December 1, 2010 @ 3:03 pm

    Any idea what can be going on??
    I have a 2003 Toyota Highlander; the problem I am having: over the summer when using my AC it was working fine and then it would start blowing hot air. Now that it’s cold and I have to use the heater it’s fine for a while then it starts to blow cold air?

  117. dennisb - Auto Tool Sales :

    Date: December 1, 2010 @ 4:34 pm

    Mari, sounds like it’s most likely the control head on the Toyota Highlander. I’ve heard of the connections being loose for the metal ribbon between the circuit boards. It may just be a matter of removing the head and inspecting for loose connections and securing – or the head may need to be replaced. Good Luck

  118. nathan :

    Date: December 1, 2010 @ 7:23 pm

    2002 Dodge Ram 1500.

    The heater takes a long time to produce hot air. Its cold air in both the defrost and vents until the engine heats up for maybe 10 min. I notice with the heater that the passenger side is always more warm than the driver side. Its the reverse with the AC, driver side is always colder than passenger.

    For a few years it always seems as though there was blockage in the path of the air traveling into the cab. Never really thought anything of it as the temperatures were fine.

    In addition, I’ve had some AC problems the last two summers. Would only put out hot air. Freon was low so charged the system one time the last two years.

    I would appreciate the advice Dennis.

  119. dennisb - Auto Tool Sales :

    Date: December 1, 2010 @ 8:45 pm

    Nathan, it’s normal for the heater to take several minutes to heat up. As far as the temperature differences for the AC and heat respectively this could be normal too. Sometimes drastic differences from side to side is from systems that are not full.

    You may also be interested in reading our article on the following link regarding airflow you mentioned –

    Low Air Flow in Dodge Rams

  120. dennisb - Auto Tool Sales :

    Date: December 6, 2010 @ 11:17 am

    Trish, no it does not. See the next page for more information on troubleshooting this particular problem. When the heat works just a little or only when more gas is given there are a couple of things to check.

    Next Page

  121. Trish :

    Date: December 6, 2010 @ 10:45 am

    I have a 2002 Mitsubishi Sypder Eclipse and the heater only blows hot when the gas pedal is down. When I’m stopped or the car is just idling it blows cold air only. Does this mean that my heater coil is bad?

  122. Cindy :

    Date: December 7, 2010 @ 11:22 am

    I have a Chrysler Sebring Conv 2001 When I turn my head lights on my heater blows very cold air. The heater works fine other than when i turn on the head lights.

  123. dennisb - Auto Tool Sales :

    Date: December 7, 2010 @ 12:29 pm

    Cindy, this is an unusual problem but not unheard of! More than likely it’s the control head. Some techs report that one way to test is to temporaily make an open orange wire that goes to the control head (by cutting it). See if the problem goes away after doing that – it’s the easiest test (without going into details). If the problem goes away, then the control head needs to be replaced and the orange wire repaired.

  124. joe :

    Date: December 14, 2013 @ 9:11 pm

    2004 toyaota van

    Driver side always cold air even when heater is on What can I do to trouble shoot this also if sitting running heats up book says that normal?
    Help please so lost.
    Thank you joe

  125. dennisb - Auto Tool Sales :

    Date: December 15, 2013 @ 2:59 pm

    Joe, the heater will not work until the car’s engine is at normal operating temperature, that is normal. If the left side never warms up there’s most likely a door control issue. Not an easy do it yourself-er diagnosis. A technician will be required Good Luck.

  126. grandma lou :

    Date: January 10, 2014 @ 12:57 am

    I read all your good advice…thank you so much..But my problem wasnt there. So, maybe you can help me. I have 1998 toyota camry. my heater works good but main vent in center of dash does not blow air. The knob indicator doesnt change to floor or main vent. Heat blow out of defroster and side vents The guage goes all the way to cold but when I turn off the heater blower the guage warms up alittle. Took it to a shop, they said I needed a flush and a new radiator. I did that but didnt help. Can you help me…Please

  127. dennisb - Auto Tool Sales :

    Date: January 10, 2014 @ 7:10 am

    There’s a big difference between the heater blowing cold and the airflow not coming out of the correct vents (mis-directed air-flow). Airflow direction (modes) have nothing to do with the heater core or radiator needing to be flushed. Actuators are a common cause on some vehicles or broken doors for the air mode not being controlled properly with the HVAC (Heating Ventilation Air Conditioning) control head. I would look at the plastic levers and cams that change the direction of airflow. I would look under the dash while operating the controls to see if anything appears to be disconnected or broken and go from there. On some cars you can look from the driver’s side floor looking up towards the center underside of the dash. On some cars some dis-assembly may be required to gain a “view” of what’s going on. Good Luck.

  128. grandma lou :

    Date: January 14, 2014 @ 3:03 pm

    Thank you so much…under drivers side was the problem…dirty and loose. It took awhile, but I’m old.
    Now their telling me I need a timing belt/chain…do I? and how much should it be? 1998 toyota camry 4cyl..thank you again for what ever help you can offer.

  129. dennisb - Auto Tool Sales :

    Date: January 14, 2014 @ 3:12 pm

    Hey glad the information helped for your Camry’s heater. The timing chain has nothing to do with the heater. Usually timing chains last around a 100,000 miles, in some cases a little more. If the chain makes a (rattling) noise, that would be an indication of wear. After the timing chain and gears are worn bad enough to make noise, the chain could jump a sprocket which could cause the engine to shut off and possibly bend valves. Good Luck.

  130. grandma lou :

    Date: January 15, 2014 @ 10:13 pm

    You’ve helped me so much. Best of luck to you, you deserve it!

  131. dan :

    Date: January 22, 2014 @ 11:04 am

    Hello… I’ve just bought a 2008 Suzuki Grand Vitara six-cylinder engine 2.7 L… The first day we went to pick it up they had washed it and done whatever upgrades we needed and was parked outside all day in cold temperatures… We turned it on and the car ran for 40 minutes straight and the heater was not warming up… The service department came and took it and said that the thermostat was clogged… So afterwards it was blowing warm air… A couple of days later the problem came back, and we took it back to them… They said that after they did the testing they notice that there was a air leak because they found some Air in the the system and air leak was caused by the radiator cap letting air and said they replaced that… About a week later the problem came back and all along most of the time when you press the gas that heat would actually come in as soon as you take your foot off the gas pedal it would blow cold air again… So we took it in again yesterday because after driving it for a week after the radiator cap was replaced the problem started coming back… They tested it and had it all day and at the end of the day said that The thermostat was faulty and it was staying in the open position always… So they replaced the thermostat… Last night I went to pick it up and it was probably about -30° outside and the car was parked outside so I turned it on with the remote starter and let it run for about 20 minutes and went back out to check and it was still cold air as soon as I press on the gas pedal it would warm up as soon as I. Take my foot off the gas… So I left it for them to see what’s happening… I spoke to the mechanic today and he said after they did a complete test for the system they see nothing wrong and that it was extreme temperatures outside and that it is normal.the car would not really be blowing hot air unless you actually drive for a couple minutes to let the engine warm up properly… But we had the car running for close to 40 minutes The end of the day last night and once your foot is on the gas would blow hot air and once it’s off at blows cold air… I spoke to them today to see what they found out and they see that they’re not seeing anything wrong and I mentioned to them what I’ve read on this blog here and other blogs on the Internet to have them check if there was any air leak again, if there was any clogging in the system, if the water pump was faulty, and if there was any blown gaskets… And they said that they have checked all of that, there was no issue that they see… Can you think of anything else that might resolve this issue please,? I feel like I’m buying a car that is not working properly from day one and they claim that everything is normal with it and now after replacing the thermostat that it should be perfectly fine that I would actually have to give it a couple of minutes of driving time to let it warm up no matter how long it’s been sitting idol and turned on… Thank you very much and I appreciate your help…

  132. Phillip Literski :

    Date: January 22, 2014 @ 11:19 am

    We have a 2006 Jeep Liberty Heat is the issue. Vehicle doesn’t blow heat until its on the freeway going over 60mph and only on defrost. Once you slow down the heat stops. What could this problem be?

  133. dennisb - Auto Tool Sales :

    Date: January 22, 2014 @ 1:11 pm

    Not an air leak but any small coolant leak can allow air to enter the system. Since your heater doesn’t work unless the gas pedal is applied the heater core could be partially clogged. The coolant pumps faster when the idle is raised. Usually the engine heats up quicker at idle rather than when the cool air from driving cools the radiator. You could compare your heater performance to another vehicle to show it is not working properly. Good Luck.

  134. dennisb - Auto Tool Sales :

    Date: January 22, 2014 @ 1:17 pm

    The coolant pumps faster when the RPM’s are raised, so maybe the heater core is clogged, the system is low or has an air lock. As far as defrost being the only functioning mode, there could be a control head issue, an actuator or a door within the HVAC case. On vacuum controlled systems there could be a vacuum leak in a hose. Good Luck.

  135. Dan :

    Date: January 27, 2014 @ 2:40 pm

    Thanks Dennis for your comment… I have done the comparison side by side with another Suzuki Grand vitara that’s a 2010 V4 engine and it’s heated up right away and they said well that was because it was a four-cylinder rather than a six-cylinder then I made them bring a 2006 six cylinder Suzuki Grand vitara and put it side-by-side next to mine and compare the two… After noticing that my car was running all day and it still Blue cold air unless the gas pedal was down and other one blue warm air after the car warmed up they decided that yes there is a problem… They’re not able to figure it out however and they have contacted Suzuki Canada and are waiting for response… One thing we noticed though is that it actually blows cold air when the fan is on high anywhere from medium to high starts blowing cold air unless you press the gas… If you keep it at blow it blows warm air actually regardless whether you press gas or not… Of course it’s warmer if you press gas but I know… Does that give you any other ideas besides the heat core being clogged up? Because when I mentioned that to them they said they already flushed the system and checked for any leaks in the system…

  136. dennisb - Auto Tool Sales :

    Date: January 27, 2014 @ 3:17 pm

    Dan, at least the comparison made them realize that your heater should work without raising the idle. I would still bet that the heater core is clogged partially or there’s a little air trapped in the system. When the RPM’s are increased the water pump, pumps coolant faster (because it is turning faster). Sometimes a heater core can be flushed with a garden hose after taking the heater hoes off and forcing water directly into the inlet and outlet pipes. If the water does not come out just as quickly as it goes in it will not perform properly. It will be less efficient because of lower capacity. An air lock can prevent the coolant from being pumped through the core also. The heater core is usually a little higher than the rest of the cooling system; so if there’s an air lock it could take more pressure for the water to be pumped up and through the heater core. A vacuum fill or a coolant funnel can be used to help eliminate air pockets. Good Luck.

  137. ike :

    Date: February 2, 2014 @ 3:52 pm

    i have a 2010 dodge ram 3500 laramie ive replaced the blend door actuator now when the heater is on the passenger side heater dose not blow heat what could this be

  138. dennisb - Auto Tool Sales :

    Date: February 2, 2014 @ 5:59 pm

    Ike, there’s not enough information to go on. I wonder why the actuator was replaced? Was it for the side in question…?

    I would have to start from the beginning checking the basics like low coolant? Air in the system etc. If the problem still persists I would check for codes in the climate control system. The door could be broken, the actuator could be bad or improperly installed…. Good Luck.

  139. ike :

    Date: February 2, 2014 @ 8:33 pm

    the actuator was replaced because there was load knocking noise in the dash behind the radio plus the defrost wasnt working, the defrost is working, now theres another clicking noise behind the glove box

  140. dennisb - Auto Tool Sales :

    Date: February 3, 2014 @ 2:38 pm

    OK. Knowing this, it sounds like two different actuators controlling two different functions.

  141. Dan :

    Date: February 3, 2014 @ 4:30 pm

    Hello again… So are Suzuki grand vitara was back in the shop today to do a flush on the system and cleaning up the pistons and a retest and they told me that it is blowing hot air now except that the only issue with it still is that there is 6° difference in The output… I’m not sure what that means and if that is normal… Do you know what they’re talking about? And what the norm is for a 2008 vehicle? The mechanic seems to think that 6° difference in output is usually too much… It was at about 12° before they did the flush… So we’ll see… they’re just waiting to hear back from Suzuki to know what they say about the 6° difference but I would like to also get your input if you can give me your input on this subject… There next step as they said would be to replace the radiator so another day again with repairs and going to the mechanic…

  142. dennisb - Auto Tool Sales :

    Date: February 3, 2014 @ 4:38 pm

    Dan, not sure what cleaning the pistons has to do with the heater. They may be talking about 6 degrees difference between the left side vents and the right side vents… I would ask them what they mean and to elaborate. It’s not uncommon for there to be a little variation from side to side but 6 degrees may be too much. On a dual zone system you can feel every degree difference as you are adjusting for comfort. Not sure why they would change the radiator… they should be considering replacement of the heater core.

  143. Dam :

    Date: February 3, 2014 @ 5:22 pm

    Hello again Dennis… So I get more information from them as to what they were saying about the 6° difference… Basically what they did is they did a side-by-side comparison between the 2008 that we have another 2006 same size engine and the difference of the 6° is not inside of the car it’s the coolant as it exits from the radiator… He saying that our car is 6° cooler than the other car was…… I don’t know what that means… Our car has never overheated while it’s been in our possession, and it warms up normally and nicely as far as the heat gauge goes… Unfortunately not the heater… so we will see if it’s better now…

  144. Dan :

    Date: February 4, 2014 @ 8:37 am

    Hi Dennis… I just spoke with the mechanic again because we took the car and it’s still not perfect and I explained to him that the heater core has to be changed… Apparently that’s what they meant by saying they need to replace the radiator… I guess it’s a language barrier between me and them… I’m dealing with a French dealership here… So just to let you know when they were talking about output they were talking about the heater core output being 6° lower than the input… Does that give you more information? It should be replaced if it’s still outputting an lower degree than the input correct? Thank you very much for your help… And also from what I understand they have to disassemble the entire – dash, empty out the coolant and the AC refill the coolant refill the AC and not just replaced The heater core but they also need to replace the aluminum piping to correct? Thank you

  145. dennisb - Auto Tool Sales :

    Date: February 4, 2014 @ 8:46 am

    That makes more sense. Remember I said “Not sure why they would change the radiator… they should be considering replacement of the heater core.” Yes, I would suspect a partially clogged heater core (the pipes are most likely part of the heater core).

  146. Catalin T. :

    Date: March 5, 2014 @ 9:46 pm

    Hi there, I’m just another pain in the neck with obviously, heater problems! I’ve got a 2008 IS220D Lexus with 85k miles and own it for 5 months only and since driving more city in last period just realised that (having dual) passenger side its cooling while driver side actually not really heating either even though I was high settings ( 30°). On motorways the temperature its getting high no problem, hence the speed I believe, plus was something else also: When cold engine, on idle, if I bring revs up between 1500-2500revs I could hear some gurgle noise as water running… which I believe must be related to each other, just guessing. Don’t know if I did right but a week ago I added “radweld” to my coolant system and was delighted to discover that the gurgles noises are gone but, still cold in the car :-(..problem not fixed! I would really appreciate your experience in this matter and maybe some step-by-step directions if its possible a cheap fix. Much appreciated.

  147. dennisb - Auto Tool Sales :

    Date: March 6, 2014 @ 7:19 am

    Catalin, we appreciate all of blog readers and tool customer’s. We make our living selling tools and our blog is our way of giving back and hopefully picking up some customers along the way. You may have read above in the article and some of the comments about how I advise NOT using stop leak, but here’s my take; The heater issue with your Lexus sounds like initially it had low coolant. Low coolant can affect one side of a dual zone system more than the other. And judging by the fact that you added Radweld (stop leak) there was a leak causing low coolant that you were trying to fix. The gurgling in the heater core is a definite sign of low coolant also. The gurgling would have went away with filling the system and getting the air out. The problem with using a stop leak product like Radweld or any other brand is that it can restrict the flow of coolant, in affect stopping up the heater core tubes reducing it’s ability to transfer the warmth of the coolant to the air in the passenger compartment. If I was working on the vehicle I would flush the system and try to get as much the the Radweld stop leak gunk out. Sometimes taking the heater hoses off and flushing directly with a garden hose is helpful. The leak needs to be fixed properly so I would pressure test the system to see where the leak is and replace any parts needed to make a professional repair. After the repair has been made, coolant has been put back in the system and there’s no air trapped I would recheck the heater and go from there. It’s possible that the heater may need to be replaced if the Radweld cannot be flushed out sufficiently. The radiator could be plugged up as well causing other issues like overheating. Good Luck.

  148. Catalin T. :

    Date: March 6, 2014 @ 3:39 pm

    Hi Dennis,
    I really appreciate your time and experience you put in for answering and you just confirm literally my doubts about Radweld or any other products of this type, I dunno what I was thinking!! I will take your advice and I’ll try 1st thing first to flush and clean the cooling system and starting from there ad you said I also read on Lexus forum about few cases like mine and some comments about Heater Matrix or blend actuator door… whatever that means, or where can be to be checked. Do you know anything about it? Thanks again for your time.

  149. dennisb - Auto Tool Sales :

    Date: March 6, 2014 @ 3:46 pm

    Catalin, an actuator is a small motor that operates a door in the HVAC (Heating and Ventilation Air Conditioning) system. It’s possible to have a faulty actuator or even a broken door. See the following article on a Chevy that had a loud actuator – Impala SS Loud AC Actuator.

  150. Catalin T. :

    Date: March 7, 2014 @ 6:49 pm

    Hi again Dennis,
    Watched the video with the loud actuator. Not my case though as no noise whatsoever but I’ve been told to check them first before I dig any deeper with my heating problem. I really appreciate your time and effort and I’ll keep you posted after the weekend when I’ll try get “dirty” and figure it out hopefully. Thanks again.

  151. dennisb - Auto Tool Sales :

    Date: March 8, 2014 @ 10:24 am

    Catalin, not sure which video you’re referring to (not one of mine). But the link to my other repair blog was intended to just show you what the actuator looks like and what it does. I understand that your’s is not making noise. They don’t have to make noise when they fail. Good Luck.

  152. Roman :

    Date: April 5, 2014 @ 12:22 pm

    i have a 2002 chrylser sebring lxi 2.7 litre convertible, about a week ago, it stopped blowing hot air through vents, the temp gauge reads normal, coolant is full, bled system just to be sure… was told it was the a/c control head (w/o auto temp), replaced that, still nothing but cold air. both lines going into heatercore are hot…its a head scratcher…any help would be appreciated?

  153. dennisb - Auto Tool Sales :

    Date: April 5, 2014 @ 2:57 pm

    I would check for codes with the climate control system and voltage readings at the blend actuator when temp setting has been changed back and forth. Good Luck.

  154. DAVID :

    Date: April 11, 2014 @ 5:22 pm

    I have a 2001 Nissan Altima that is due for maintenance this week (scheduled CV joints, new belts, O2 sensors). Now the car seems to have some overheating issues. I replaced the radiator and thermostat 3 months ago because a small crack in the radiator, it seemed to have fixed it for a few months. Now presently there is a slight squealing noise in the AM when I start it to go to work. This was not an issue as I assumed it was the AC pulley with a flat bearing. It would do it every now and again when I turned on the A/C but would sometimes go away if the RPM’s slowed. Now the A/C button can be depressed and the temp gauge rises, even if the A/C button is depressed or not. The A/C compressor still blows very cold and the heater works well as well. The A/C was working for a bit then it started to not work, instead blowing room temp air and the temp gauge was rising to the point of overheating. The heater was turned on to see if it helped cool the vehicle and it did not. My wife noticed the heat gauge rising only when you accelerated to fast or when the gas pedal was not depressed at all. Since I have replaced the thermostat and the radiator I am leaning toward replacing the water pump, should I look into some other cause of the overheating issue?

  155. dennisb - Auto Tool Sales :

    Date: April 11, 2014 @ 5:56 pm

    David, you may have several issues. The squealing is most likely a loose belt. The overheating is most likely low coolant. I would pressure test the cooling system to see what is leaking, The water pump may have a leak or it could be something else. The AC should not blow cold when it’s been turned off with the button. I would do some testing and make sure the clutch is disengaging as it should. Maybe let the tech doing the maintenance work that you’ve scheduled look into these issues. Good Luck.

  156. DAVID :

    Date: April 11, 2014 @ 6:10 pm

    There is not any liquid leaking, I did the pressure test all was good. The A/C does not blow cold when the button is depressed but did stop blowing cold when the temp gauge beagn to rise to an overheating temp.

  157. dennisb - Auto Tool Sales :

    Date: April 12, 2014 @ 9:56 am

    David, thanks for clarifying. It’s possible that there’s a cooling fan issue. If the AC condenser (similar to the radiator but for the AC) is not getting enough airflow the AC will not work well (maybe just when driving down the road). And if the cooling fan is not working the coolant in the radiator may only get enough airflow to keep the engine cool when driving at highway speeds. Good Luck.

  158. Kimberly :

    Date: May 23, 2014 @ 6:44 pm

    I have a 2010 Chrysler Sebring. The A/C will only blow out cold air if is parked in a cool location prior to driving. Secondly, the air and heat cut off when you push the control to “high” or “max” out put. Do I need a new compressor? Or does this sound like an electrical problem?

  159. dennisb - Auto Tool Sales :

    Date: May 24, 2014 @ 9:30 am

    Kimberly, sounds like two different problems. I would check the AC gauge readings for the first problem of the AC not cooling well. See our AC gauge readings explained article for information on what the readings mean. The second problem has nothing to do with the compressor. It sounds like an electrical issue as you mentioned. I’d get an electrical wiring diagram for your vehicle and start testing circuits to pinpoint that problem. Good Luck.

  160. Wise Auto Tool Blog » Water Leaking Into Car Floorboard – Wetting Carpet :

    Date: August 1, 2014 @ 8:20 am

    […] of clear water then the heater core is likely the culprit. See the following repair article on Car Heater Blows Cold Air for more on that […]

  161. Mike :

    Date: November 19, 2014 @ 10:22 am


    Im bringing this back from the dead persay, but I have been blessed with working on my buddies 00 Sebring Convertible. (fun..) and we did a ton of work to it just before winter hit. We replaced his thermostat because the car was overheating to the point that he had to shut the car off all the time. Now, it fixed that issue. We replaced the thermostat with a OE temp one from Autozone. Now he just called me and told me he is having the “Heater works when idling but driving it cools off” issue. Do you think we got a bad thermostat, or could there be a new issue? 2.5 Ltr V6 just incase. Thanks!!

  162. dennisb - Auto Tool Sales :

    Date: November 19, 2014 @ 10:27 am

    I’d make sure the cooling system is full and there’s no air in the system. Good Luck.

  163. catherine :

    Date: January 1, 2015 @ 11:04 am

    My 1996 pontiac Bonneville only has heat when I add more gas

  164. dennisb - Auto Tool Sales :

    Date: January 1, 2015 @ 3:00 pm

    Catherine, adding gasoline has no relation to the car’s heater unless you’re topping off the cooling system’s overflow bottle while you’re at the pump. Good Luck.

  165. bob :

    Date: January 2, 2015 @ 4:22 pm

    Hi Dennis,

    I have an 01 Sebring sedan with 2.7l and the heater isn’t blowing warm air. Both heater core hoses are hot and the engine is not overheating. What is the likely cause?

  166. dennisb - Auto Tool Sales :

    Date: January 2, 2015 @ 4:35 pm

    Normally just low coolant and maybe air in the system. But if both hoses are very hot, perhaps there’s an actuator problem controlling the blend door. The core could be partially restricted also. Good Luck.

  167. brittni :

    Date: January 8, 2015 @ 9:04 pm

    I have a 1999 Ford Taurus an just put a new Thermostat in because the heat didn’t work. Now it only blows hot air when I reach 4000 rpms an when this happens the temperature gauge drops to cold otherwise it blows cold air…help?

  168. tiegua anderson :

    Date: January 23, 2015 @ 5:44 pm

    On my Dodge Neon when I turn on the heat it blows out cold air. Then I got it fixed. It blows out heat when im driving it but when I’m at a stop light, it get blows out cold air again. I know some cars do that but not all cars and I want to know the problem and what can I do to get this fixed. It’s a 2000 Dodge Neon.

  169. dennisb - Auto Tool Sales :

    Date: January 26, 2015 @ 8:03 am

    Since it didn’t stay fixed; I’d guess that there’s a coolant leak that is affecting the heat again. Low coolant is the most common cause of a car heater not working properly. I’d check the coolant level. If it’s low I’d pressure test the system and look for coolant leaks. Then repair the leaks. If leaks are not fixed, just filling the radiator (cooling system) will only be a temporary solution. Good Luck.

  170. Bryan :

    Date: February 6, 2015 @ 11:06 am

    I have a 2003 Jeep Liberty it blows warm air if you use settings 1 and 2 but once you go past that using 3 and 4 it starts to blow cold air any ideas?

  171. dennisb - Auto Tool Sales :

    Date: February 6, 2015 @ 11:17 am

    When on the heater setting, it’s normal to a point for the air to be warmer on slower fan speeds. I’d check all the normal things like coolant level, air in the system etc. Good Luck.

  172. harry :

    Date: February 13, 2015 @ 9:26 pm

    I have a 2004 Sebring, v6. When I shut the car off today I noticed some smoke coming from under the hood. Also the heater only got warm when the gas pedal was depressed. Had the car towed home. The tow truck driver said, I had a small antifreeze leak? I did see that it was slightly wet next to the resovoir?? Big problem??

  173. ernie :

    Date: February 14, 2015 @ 8:12 am

    I have a 99 mustang convertible 3.8 and the heater will blow hot air for the first 20 minutes but once the temperature gauge gets to about mid it stops blowing hot and blows cold the water in the radiator also gets cooler please help…..

  174. dennisb - Auto Tool Sales :

    Date: February 14, 2015 @ 10:19 am

    In extreme cold weather. it’s possible that an incorrect temp thermostat could be the problem. The engine should be running at around 210-212 degrees. THis is best for the engine and the heater system. Good Luck.

  175. dennisb - Auto Tool Sales :

    Date: February 14, 2015 @ 10:21 am

    Low coolant can cause the heater not to work properly. I’d pressure test the system and pinpoint the leak. Could be a small problem or a big problem depending upon what’s leaking. Good Luck.

  176. Raul Alfaro :

    Date: March 11, 2015 @ 11:16 pm

    Grand Cherokee 2011. My A/C blower speed is varying from max to min without any control. Originally, passenger side air was hot while driver side was cold, so the dealer diagnosed low level of refrigerant and they recharged it. After that worked, the blower began to fail, and what’s more, now it is not heating when hot is selected. Any idea? They already replaced the resistor and the blower motor without any result. The dealer diagnosed the lack of heating as a failure in one of the gates (doors), that sounds logical, but they are lost figuring out what is causing the blower speed variation. I wonder if both failures could be related.

  177. dennisb - Auto Tool Sales :

    Date: March 12, 2015 @ 7:01 am

    Some variation in blower speed sound can be normal depending on how much electrical load is on the charging system. I would check the charging system and battery for starters. The electrical connections for the blower and resistor are a source of problems sometimes, so I would check to see if they appear burned (or overheated) which would indicate a poor connection that can affect performance. After the gate (door) has been replaced I would recheck the system to see if you’re still experiencing any issues. If so I would look at the climate control data with a scan tool while the remaining issues are present. Good Luck.

  178. Gillian - SouthNZ :

    Date: August 16, 2015 @ 3:40 am

    Hi Dennis, I am hoping you can help. My husband and I have recently purchased a 1991 Mazda Parkway bus which has been converted into a motorhome. The heater in the bus has warm air coming out ok through the window demister vent (non AC)but we only get cold air through the passenger and driver vents. A new thermostat has been installed recently and the coolant flushed and replenished. This makes for very cold drives in the South of South Island of New Zealand. Any advice would be greatly received. Many thanks

  179. dennisb - Auto Tool Sales :

    Date: August 16, 2015 @ 9:45 am

    Could be a partially blocked heater core or air control door/actuator problem. Unfortunately this problem would take some hands on to check out, which puts me at a disadvantage. Good Luck.

  180. Ekpadi :

    Date: August 23, 2015 @ 11:27 am

    Control to select vent/floor heat/defrost does not change air blowing position. Stuck on vent no matter what position the selector is on. How can I trouble shoot. Is there a vacuum hose or cable that may have broke or come loose under the dash? Or do I need to replace the controler

  181. dennisb - Auto Tool Sales :

    Date: August 24, 2015 @ 9:13 am

    I’d check a repair manual for how your specific vehicle/HVAC controls are set up and go from there. Each type of vehicle are different. Good Luck.

  182. Ricky Espinoza :

    Date: August 24, 2015 @ 10:06 pm

    I have a 2003 Ford Mustang. I hadn’t been using my AC because it would leak water inside the car on the front passenger side below the dash. I thought it to be the heater core, but the other day I bypassed it. Well to my surprise its still leaking water. What could the problem be?

  183. dennisb - Auto Tool Sales :

    Date: August 25, 2015 @ 7:19 am

    Ricky, coolant is usually green NOT clear. Coolant also has a sweet odor. A coolant leak from the heater core will leak all the time not just when you’re running the AC. Condensation from the evaporator is what you have from a stopped up drain or a leaky seal around that drain. Here’s several articles I’ve written on the subject.
    AC Water Leaks Inside Car – How to Fix
    Water Leaking Into Car Floorboard – Wetting Carpet

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