Why wouldn't the heater and air conditioner blower work on a car? The most common cause of a heater and air conditioner blower not working on a car is a faulty blower motor. Without the blower motor, the system is unable to push air through the vents inside the vehicle. What causes a car heater to malfunction? What makes an air conditioner blower not come on? How can you tell if you have a faulty auto air conditioner clutch? Another cause of the heater and air conditioner not blowing inside the car is a faulty transistor. If the transistor begins to fail, the system often blows only on the highest setting. A clogged motor or fan can also cause operation issues. As dirt and debris build up on the system, this can cause the components to seize up or work less than optimally. Where is the cabin air filter located in your car? Possible locations for the cabin air filter include in the outside air intake, between the blower and the HVAC case, or over the blower at the back of the ...