General Information

The purpose of the Air Conditioning (A/C) system is to provide cool air and remove humidity from the interior of the vehicle. The vehicle operator can activate the A/C system by placing the mode switch in one of the following positions: Max A/C, A/C, Bi-Level, Blend, and Def. The A/C system can operate regardless of the air temperature setting.

Regardless of the selected A/C mode setting, a request is made to the Powertrain Control Module (PCM) to turn on the A/C compressor clutch. The request is sent to the PCM through the A/C request signal circuit and A/C high pressure switch from the HVAC control assembly. On vehicles equipped with a diesel engine, the A/C request is sent to the PCM through the A/C request signal circuit and A/C high and low pressure switches from the HVAC control assembly. Power and ground are provided to the HVAC control assembly by the ignition 3 voltage and ground circuits.

The PCM turns on the A/C compressor by providing a path to ground through the A/C compressor clutch relay control circuit for the A/C compressor clutch relay. The ignition 1 voltage circuit provides power to the A/C compressor clutch relay control. Once the relay contact closes its internal switch, power from the battery positive voltage circuit is provided to the A/C compressor clutch through the A/C compressor clutch supply voltage circuit. Whenever the compressor is turned off, the A/C clutch diode prevents a voltage spike from damaging the compressor clutch coil. The ground circuit provides a pathway to ground for the compressor and diode. Both the A/C request signal and A/C clutch relay control circuits are grounded by the ground circuits.