A/C on Signal

A/C On Signal, Pressure Transducer And Clutch Control Relay:

This signal indicates that the A/C control switch is turned "ON" and that the A/C pressure sensor is functioning properly. The ECM uses this signal to adjust the idle speed, and on some models engages the A/C compressor clutch. If this signal is not available to the ECM, the A/C compressor will be inoperative and a Code 66 will result.