Blower Motor: Description and Operation
POWER MODULEThe blower motor power module is only used in vehicles equipped with Automatic Temperature Control (ATC). It is located on the lower right side of the HVAC unit housing, and is controlled by the Body Control Module (BCM).
The power module receives pulse width modulated (PWM) signals from the BCM. The power module varies voltage to the blower motor for different blower speeds based on the ATC software. There are 14 selectable speeds, while the Auto mode provides 256 variations.
BLOWER MOTOR
The blower motor and blower wheel are located in the passenger side end of the HVAC housing, below the glove box module. The blower motor controls the velocity of the air flowing through the HVAC housing by spinning a squirrel cage-type blower wheel within the housing at the selected speed. The blower motor and blower wheel can be serviced from the passenger compartment side of the housing.
The blower motor will only operate when the ignition switch is in the ON position, and the a/c heater mode control switch is in any position, except OFF. The blower motor circuit is protected by a fuse in the junction block. On models with the standard manual temperature control system, the blower motor speed is controlled by regulating the battery feed through the blower motor switch and the blower motor resistor. On models with Automatic Temperature Control (ATC) system, the blower motor speed is controlled by using Pulse Width Modulation (PWM). The blower motor power module adjusts the battery feed voltage to the blower motor, based upon an input from the blower motor switch, through the ATC control module. Pulse width modulation of blower power allows the blower to operate at any speed from stationary, to full speed.
The blower motor and blower motor wheel cannot be repaired, and if faulty or damaged, they must be replaced. The blower motor and blower wheel are not serviced separately and must be replaced as an assembly.