The heater and A/C programmer is attached to a bracket. The bracket is located next to the right end of the heating, ventilation, and air conditioning (HVAC) module assembly, behind the glove box. The heater and A/C programmer provides the controls for temperature regulation.

The heater and A/C programmer controls an electric actuator. The electric actuator adjusts the air mix valve position in order to blend cold and warm air. Vehicles with dual zone (CJ2) have 2 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 in order to monitor the actual valve position.

The heater and A/C programmer operates the 4 vacuum solenoids. The solenoids control vacuum to the various vacuum actuators. The vacuum actuators control the following components:

The heater and A/C programmer also controls the park brake release actuator. The powertrain control module (PCM) sends a Class 2 serial data message to the heater and A/C programmer whenever the transmission is shifted out of PARK or NEUTRAL. The heater and A/C programmer will then supply vacuum to the park brake release solenoid, which releases the park brake.

The heater and A/C programmer sometimes is referred to as the air control module (ACM). This reference is commonly used by a scan tool and by the diagnostic trouble codes (DTCs).