Power Module (Front)
A blower power module is used on this model when it is equipped with the optional Automatic Temperature Control (ATC). See Fig 1. Models equipped with the standard manual HVAC control use a blower motor resistor instead of the blower power module. The blower power module is installed in a mounting hole in the evaporator housing, directly behind the glove box opening of the instrument panel. The module consists of a molded plastic mounting plate with 2 integral connector receptacles. Concealed behind the mounting plate within the evaporator housing is the power module electronic circuitry and a large finned, heat sink. The module mounting plate is secured with 2 screws to the evaporator housing and is accessed for service by rolling down the glove box from the instrument panel. The power module heat sink will get hot when in use, Do not touch the heat sink if the blower motor has been running. The blower power module cannot be adjusted or repaired and if faulty, or damaged, it must be replaced.
The blower power module is connected to the vehicle electrical system through a dedicated take out and connector of the instrument panel wire harness. A second connector receptacle receives the pigtail wire connector from the blower motor. The blower power module allows the microprocessor based Automatic Temperature Control (ATC) HVAC control module to calculate, and provide infinitely variable blower motor speeds based upon either manual blower switch input or the ATC programming using a Pulse Width Modulated (PWM) circuit strategy. The PWM voltage is applied to a comparator circuit which compares the PWM signal voltage to the blower motor feedback voltage. The resulting output drives the power module circuitry, which adjusts the voltage output received from the blower motor relay to change or maintain the desired blower speed. The blower power module is diagnosed using a DRBIII® scan tool.