Through Model Year 2011

Front Blower Motor Power Module

• Automatic Temperature Control (ATC) shown. Manual Temperature Control (MTC) similar.







Description

Both the Automatic Temperature Control (ATC) and Manual Temperature Control (MTC) heating-A/C systems use a blower motor power module to control the front blower motor speed.

The front blower motor power module is mounted to the HVAC housing, on the passenger side of the vehicle. The blower motor power module consists of a molded plastic mounting plate (1) with two integral wire connector receptacles (3). Concealed behind the mounting plate is the power module electronic circuitry and a large finned heat sink (2).

The blower motor power module is accessed for service from underneath the instrument panel.

Operation

The blower motor power module is connected to the vehicle electrical system through a dedicated lead and connector of the instrument panel wire harness. A second lead and connector of the instrument panel wire harness is connected to the blower motor.

On the Automatic Temperature Control (ATC) system, the blower motor power module allows the microprocessor-based A/C-heater control to calculate and provide infinitely variable blower motor speeds based upon either manual blower switch input or the ATC programming.

On the Manual Temperature Control (ATC) system, the blower motor power module allows the microprocessor-based A/C-heater control to provide an infinite amount of blower motor speeds throughout its operating range, based upon blower switch input.

Both the ATC and MTC systems use a Pulse Width Modulated (PWM) circuit strategy. 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 provides a linear output voltage to change or maintain the desired blower speed.

The blower motor power module is diagnosed using a scan tool.

The blower motor power module cannot be adjusted or repaired and must be replaced if inoperative or damaged.