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 pressing the A/C switch. The A/C system can operate regardless of the temperature setting, however, recirculation is only available when the HVAC control assembly is in the MAX A/C mode.

The Powertrain Control Module (PCM) will operate the A/C system automatically in FRONT DEFROST mode to help reduce moisture inside the vehicle. The A/C LED will not illuminate unless the driver presses the A/C request switch on the HVAC control assembly. The A/C system may be running without the A/C LED indicator illuminated when in FRONT DEFROST mode.

Regardless of the selected A/C mode setting, a request is made to the Body Control Module (BCM) to turn on the A/C compressor. The request is made by the HVAC control assembly to the BCM, through the A/C request signal circuit. When the BCM receives the signal from the HVAC control assembly, the BCM then sends a class 2 message to the PCM through the class 2 serial data circuit.

The PCM grounds the A/C clutch relay control circuit and the A/C compressor clutch engages. Power is provided to the HVAC control assembly by the ignition 3 voltage circuit. Ground is provided by the ground circuit. The PCM turns on the A/C compressor by providing a path to ground through the A/C clutch relay control circuit for the A/C compressor clutch relay. Power is provided to the A/C compressor clutch relay from the underhood fuse block. Once the relay closes its internal switch, battery voltage 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 compressor clutch diode prevents a voltage spike from entering the vehicles electrical system. The A/C clutch relay control circuit is grounded internally within the PCM.

"For the description of RPO code(s) shown in this article or any of the images therein, refer to the RPO code list found at the Vehicle/Application And ID." RPO Codes