DeVille V8-4.6L VIN Y (1998)
Control Module HVAC: Description and Operation
Air Conditioning Programmer (ACM)
The heater and A/C programmer 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 heater and A/C programmer
provides the controls for temperature regulation.
The heater and A/C programmer controls an electric actuator that adjusts the air mix valve position to blend cold and warm air. Vehicles with dual zone
(CJ2) have two electric actuators that mix the air independently of each other. 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 heater and A/C programmer also responds to operate the four vacuum solenoids. The solenoids control vacuum to the various vacuum actuators
which in turn control the air inlet valve, A/C DEFROST valve and the UP/DOWN valve. An additional function of the heater and A/C programmer is to
control the park brake release actuator. The PCM sends a Class 2 serial data message to the heater and A/C programmer. This message is sent when the
transmission is shifted out of PARK or NEUTRAL.
