3 Ways Your Car's Blower Can Fail
Your car's air conditioning system includes many of the standard components you can find in a traditional home HVAC system. These include a compressor, condenser and evaporator coils, and a blower motor to push cooled air into the cabin. Many automotive air conditioning problems prevent the system from cooling air, but blower failures can be just as frustrating.
Symptoms of a problem with the blower can vary from erratic fan speed control to air that remains stubbornly still. The three issues below have different symptoms, but you can trace them all back to your car's blower or vents.
1. No Air Movement At All
The most obvious symptom of a failing blower is a fan that doesn't work at all. For vehicles with automatic climate control systems, try using manual mode with the highest fan setting. If you still don't get any air from your vents, then there's a good chance that your blower has failed. Note that almost all vehicles use one fan for the whole car, so blower problems should affect all vents.
For suspected blower problems, always start by checking the fuse and relay. If these check out, your issue may lie with the blower motor itself. Another common culprit is the blower motor resistor. This simple electrical component controls the amount of power that your blower motor receives, allowing your fan to run at variable speeds.
2. Erratic or Inconsistent Fan Speed Control
For most cars, two components control the HVAC fan speed: the blower motor resistor and the climate control dash unit. The dash unit includes the physical controls that you use to set your desired temperature and fan speed. This unit sends a signal to the blower resistor, which then varies the input power to the blower motor.
Fan speed problems more commonly arise from a bad resistor, although a faulty control unit is also a potential issue. Since the resistor can sometimes be challenging to reach (many manufacturers locate it below the dash), it's best to allow a professional to diagnose the underlying cause of your problem.
3. Inconsistent Airflow From One or Two Vents
One final problem can masquerade as a blower failure, but it has a very different cause. Any problem with your blower motor should consistently affect all of the vents in your car. If you notice inconsistent airflow from a single vent, your blend door is more likely at fault. The blend door controls the mix of cold and warm air that you feel inside of your car.
A blend door actuator that isn't working correctly may block some or all of the airflow from the vents that it controls. In this case, those vents may produce weaker airflow, or their air may seem less cold than other vents. For more information, contact an auto AC repair service.