The heater blower is made up of a motor and a fan that together are responsible for blowing air into the passenger compartment of a car. The heater blower uses a series of resistors to change the speed of the fan and control the rate of air flow.
The heater blower is usually located beneath the car hood or under the dashboard next to the air conditioning console. The most common indication that the heater blower is not functioning properly is if the rate of air flow cannot be changed using the dashboard air conditioning control panel. Heater blowers that contain a shorted-out or faulty resistor are only able to operate on a high speed. The resister component for heater blowers is an affordable part that can be installed without the help of a mechanic.
Other indications that a heater blower is not operating correctly and needs to be changed are abnormal noises issuing from the air conditioning console when it is turned on and inconsistent air flow from the air conditioning vents. Additional reasons for a heater blower malfunctioning are animals building nests in the heater blower fan causing it to jam, or fluid leaking from the car's heater core or evaporator and falling on the heater blower motor.