A/C Request Signal

The A/C control assembly provides a 12 volt A/C request signal to the Body Control Module (BCM). The BCM then transmits the request through the Class II serial data circuit to the Powertrain Control Module (PCM). The PCM uses this information to adjust the idle speed before turning on the A/C clutch. If this signal is not available to the PCM, the A/C compressor will be inoperative. Refer to PCM Controlled A/C Circuit Diagnosis for A/C clutch wiring diagrams and diagnosis of A/C clutch electrical system. When diagnosing the A/C controller and refrigerant portion of the HVAC system, the Cooling Insufficient, A/C System diagnosis in Heating, and Air Conditioning should be used.