Car AC Airflow Problems

Often when faced with car AC airflow problems, DIY car mechanics may think that it is a blower motor problem.

Although this is one of the possibilities there are several others that can affect the airflow from the air-conditioning duct-work.

It is the job of the Blend doors to make sure that the air is at the right temperature and is also being discharged from the correct air ducts.

The driver at the climate control center controls the blend doors. But what happens when the driver selects the temperature and direction of the air. But the results are different than expected.

Well, if the blower motor is running but no air comes out of the ducks the problem can be a stuck or inoperative airflow control or blend door.

Types of AC airflow controls

Also used on both newer and older vehicles would be vacuum operated blend doors. This system uses engine vacuum to operate vacuum diaphragms. This in turn will push or pull the direction ductwork into the proper position.

The last type of air, flow control would be the use of electrical motors that actually control the blend doors themselves. In this case, when the driver selects the desired temperature the climate control module sends a signal to a remote mounted electric motor that performs the adjustment.

Car AC airflow problems

Even the cable can experience problems such as binding or kinking that reduce the efficiency of the opening and closing of the blend doors.

Often when this condition occurs, the driver will feel a spring back on the control lever itself.

When you experience this problem inspection of the cable and possible replacement of the component will be needed.

car AC airflow problems on vacuum operated systems usually stem from missing vacuum inputs. No vacuum signal can cause the air to dump behind the dash and flow very weak from all of the vents.

When you hear your blower motor running, and you have weak or misdirected airflow checking the vacuum source is a good first step. Vacuum diagrams of your air-conditioning system can be obtained in your online car repair manuals.

An example of one of the most troublesome ones is pictured to the right. This is what the mid 90's GM actuator motor looks like.

Many of these electronic controlled actuator motor's just plain failed. When this happens, the driver may not be able to control temperature or the direction of the airflow.

Since the diagnostic tree charts vary with the model year and specific application it is recommended that you follow the diagnostic steps for your specific vehicle.

In some cases, when you replace these AC airflow motors. They will have to be calibrated for proper operation.

The main lesson to learn is if you have car AC airflow problems and your blower motor is running your diagnosis should be heading for a blend door or AC airflow problem.

Identifying what type of blend door system you have, whether it be cable operated, electrical motor, or vacuum type will lead you to the correct diagnostic steps.

Also keep in mind on vehicles older then twenty years or so, that deterioration of the sealing strips on the door (usually rubber) may also be a problem and should be inspected.


Give this car ac airflow problems page a Then learn some more about car ac systems.


Learn all about your automobiles air conditioning system on the main page for AC Systems. This next link takes you from car ac airflow to air-conditioning theory


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