Control Module HVAC: Description and Operation

AIR CONDITIONING PROGRAMMER (ACM)
The ACM is attached to a bracket located next to the right end of the HVAC module assembly behind the glove box and can be identified by the electrical connectors attached to it. Within the case are the functional components described below. The ACM provides the controls for temperature regulation.

The ACM controls an actuator that adjusts the air mix valve position to blend cold and warm air. The motor is reversible and moves a rotary shaft which drives the air mix valve link. The motor also provides a position sensor signal to monitor actual valve position.

The ACM also responds to operate the four vacuum solenoids. The solenoids control vacuum to the various vacuum actuators which in turn control the air inlet (recirc.) valve, A/C DEFROST valve and the UP/DOWN valve. An additional function of the ACM is to control the Park Brake Release Actuator. The PCM sends a Class II message to the ACM. This message is sent when the transmission is shifted out of Park or Neutral. The ACM will then apply vacuum to the Park Brake Release Solenoid and release the park brake.