A/C Signal: Description and Operation
DESCRIPTIONThe air conditioning (A/C) signal is used to inform the Engine Control Module (ECM) that a request for air conditioning has been made.
OPERATION
When the A/C switch is closed, pin A26 of the ECM is grounded, informing the ECM that the air conditioning has been turned on. The ECM then controls the compressor relay and adjusts idle speed to compensate for compressor load.