A/C Request Signal
WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
The A/C system can be engaged by pressing the A/C switch. The A/C switch will illuminate when the A/C switch is pressed to the ON position. The MAX A/C, front defroster and defog mode selections will also automatically run the A/C compressor. The A/C LED will not illuminate in these modes of operation. The HVAC control assembly sends a A/C request message to the Body Control Module (BCM) which sends a class 2 message to the Powertrain Control Module (PCM). The A/C compressor clutch relay control switch in the PCM closes creating a ground and energizing the A/C compressor relay coil which closes the A/C compressor clutch relay switch energizing the A/C compressor clutch.