Low Air Flow From AC Vents – Auto Repair Tips/ToolsJune 27, 2009 9:52 am Air Conditioning, DIY, How To Auto Repair
Leaves accumulated near the fresh air intake can enter the car’s evaporator case.
© DenLorsTools.com Summary: Article on low flow from air conditioning vents in cars. Neglected cabin air filters are the leading cause of this issue. Although, there are several things that can cause low airflow from a vehicle’s air conditioning system. The strongest blowing vents are the middle ones with the setting adjusted to maximum or recirculate. On the max setting, the air is recirculated in the passenger compartment. Obstructions can include leaves, loose articles from the glove-box, a broken or out of position door in the Heating Ventilating & Air Conditioning (HVAC) case.
Most people don’t realize that many vehicles come with a cabin air filter. One of the first things to check for when experiencing low airflow is to see if the car has a cabin air filter and if it does, check to see if it’s dirty. The cabin air filter is very similar to a home air-conditioning filter just on a smaller scale. Like the home air-conditioning filter, the cabin air filter for a car can become dirty and restrict air flow. In addition to the dirt and pollen, a car’s air-conditioning filter can also be obstructed by leaves. This is especially true if the car is regularly parked under trees. A quick check in the vehicles owner’s manual should reveal if the car has one and where it is located.
Usually cabin air filters are found in the following locations
- Many BMW car’s and some others are located under the hood just below the windshield.
- Numerous autos have the filter located behind the glove box.
- On many Chrysler vehicles there’s a thin removable panel on the passenger side, lower portion of the evaporator case (behind dash panel) to access the filter. This is a good place since debris like leaves will settle in the bottom and can be easily cleaned out when the filter is being changed.
Glove compartments usually aren’t sealed off, this can allow items to fall out the back.
Overflowing glove compartments – noisy blower motor
The air return is usually located behind the glove box. Sometimes with an “over full” glove box; contents like napkins, vehicle registration or anything else can fall out of the back of the compartment when it is closed and can be drawn into the air return. If this happens, the air flowing into the return can be restricted causing less air to blow out of the vents. If debris ends up traveling all the way to the blower fan, vibration and a low flow will be the result. Just one leaf in a blower motor fan can cause noise and vibration. On some cars the glove box door can be unhooked and swung down to check for articles that may have fallen out of the glove compartment; with some luck the obstruction could be on the outside of the air return. Other times the blower motor may need to be removed and any foreign debris removed. The fan attached to the blower motor is round and sometimes called a squirrel cage, due to it looking a lot like a hamster exercise wheel. On numerous vehicles the blower motor is fairly simple to remove, with others it can be quite a task. If it can’t be determined how big of a job it is to remove the blower motor by just looking at it, a service manual can be checked to see how involved it is on the particular model. Even the labor time can indicate if it’s an easy job or more involved. A lot of times a noisy or vibrating blower motor is remedied simply by removing it, cleaning it and reinstalling it.
More serious problems
It’s good to start with the basics but if the cabin air filter and the blower are not the cause of low airflow, then an actuator or HVAC door could be the problem. Sometimes an actuator which is a small electric motor or vacuum operated device for moving the doors within the case can fail. Without the actuators working properly the air isn’t directed the way it’s supposed to go causing low airflow or incorrect airflow. Other times the door itself can break causing similar problems. If the fresh air/recirculate door breaks, it can sometimes fall down over the blower fan almost restricting the airflow completely.
Question – I have no airflow. Someone told me the resistor might have gone out. The blower motor does not run at all, can you help?
Answer – Usually with a bad blower resistor, the high speed would still work; so I wouldn’t suspect that is your problem. The most common causes would either be a bad blower motor or a poor connection at the electrical plug (that goes to the blower motor).
Question - I have a 2006 Pontiac GTP, I can’t see any screws holding the blower motor – how do I change it?
Answer - The blower motor plastic housing has to be cut to remove it. There is a thin groove to guide the cut, use a hot knife to easily cut it. Be careful and stay within the groove though because the plastic housing will be re-used with the replacement motor.
Question - I have plenty of airflow, but the air is not cold – any suggestions?
Answer -Start with checking the pressure readings for the AC system. Most of the time if the air conditioning is not cold, it’s because of low refrigerant.
Question – I have a 2003 Jeep Grand Cherokee with dual zone AC. Why would the passenger side AC be hot and the driver’s side is cold?
Answer - Sounds like there is either a bad actuator or a faulty blend door, see our auto repair tech article covering this common problem with Grand Cherokee broken blend doors.
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