A/C Signal: Description and Operation

PURPOSE:
This signal indicates that the A/C control switch is turned "ON" and the pressure switch is closed.

OPERATION:
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 engine idle may be rough when the A/C compressor cycles. In some cases the A/C compressor will be inoperative.