A/C Switch

When A/C switch is in ON position, it sends a signal to PCM to inform PCM that A/C has been selected. PCM adjusts idle speed to a preprogrammed RPM through Idle Air Control (IAC) motor to compensate for increased engine load.

When A/C function is selected (A/C switch on), PCM receives A/C request signal from evaporator switch. This signal indicates evaporator temperature is in the proper range for A/C operation. A/C request signal is used by PCM to activate or deactivate A/C compressor clutch through A/C relay and to determine proper idle speed through IAC motor position.

If A/C low pressure switch opens (indicating a low refrigerant level) or if evaporator switch opens (indicating evaporator is not in proper temperature range), PCM will not receive A/C request signal and PCM will remove ground from A/C relay, deactivating A/C clutch.