With the ignition switch on, voltage is supplied through the A/C Blower fuse and the ignition positive voltage circuit to the heater-A/C control. The voltage to the temperature signal circuit is varied from B+ to approximately 1.5V by the temperature control potentiometer in the heater-A/C control module. The heater-A/C control receives ground through G201 and the temperature control actuator motor receives ground through G202.

Control of air through the system is regulated by vacuum. At various positions of the heater-A/C control, mode valves mix and direct cooled, heated and outside air through the air ducts.

The air temperature valve determines how much air flows through the heater core, which determines the temperature of the air to the outlets. In the C60 system the air temperature valve is controlled by the single temperature control actuator motor . In the CJ3 system, the air temperature is controlled separately for each side of the vehicle through individual temperature control actuator motors. The position of the air temperature valve(s) is determined by the voltage level output from the heater-A/C control.