Air Conditioning Switch: Description and Operation

When A/C operation is required by the driver, the ECU activates the system. When the system is turned on by the driver a signal is sent to the ECU (via the A/C switch). The ECU then energizes the A/C relay which in turn activates the compressor clutch (if the A/C low pressure switch is closed). The ECU uses this system to compensate for added engine load from the compressor.