Control Module HVAC: Description and Operation

A/C Blower Motor Speed Control
The A/C blower motor speed control is located on the A/C evaporator housing, in the engine compartment.
- The function of the A/C blower motor speed control is to convert low power signals from the electronic automatic temperature control module to a high current, variable ground feed for the blower motor.
- Blower motor speed is infinitely variable and is controlled by the electronic automatic temperature control module software.
- A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

Rear Audio/Climate Control Module
The rear audio/climate control module is equipped on limousine (long wheel base) vehicles and is mounted to the back of the rear seat backrest. The rear audio/climate control module converts an input from the rear audio/climate control switch, then signals the Audio Control Module (ACM) via the Audio Corporate Protocol (ACP) bus. The ACM then signals the EATC module over the J1850 communications network (standard corporate protocol [SCP] bus).