For 1990-2009 cars

The A/C switch controls the operation of the air conditioning system. The A/C switch is mounted on the heater control unit. In all modes, the A/C switch must be on in order to engage the compressor. When the A/C switch is pressed, the switch signals the A/C compressor control module that air conditioning system operation has been requested.

Air conditioning output temperature is controlled by the position of the temperature control lever on the heater control unit. A cable connects the lever to the air flow door in the heater case. The position of the door controls the air flow through the heater core, as the temperature control lever is moved through its full movement.