Compressor Clutch Relay: Description and Operation

A/C Relay

PURPOSE
Controls A/C compressor operation.

LOCATION
Center of firewall in engine compartment.

OPERATION
When the ECU receives an A/C "ON" signal, it in turn sends a signal to switch "ON" the A/C relay and also energizes the fast idle control device (FICD) solenoid valve. The valve is in line between the air filter housing and intake manifold. When the valve is open, air bypasses the throttle valve and thereby raises the idle speed to compensate for the extra load created by A/C operation. Neither the A/C relay nor the FICD set trouble codes if they are faulty.

The ECU initiates A/C-cut control under any of the following conditions:
^ Engine coolant temperature surpasses 115° C (239° F).
^ Engine idle speed is below 650 rpm.
^ During certain specified high-load operations.
When the ECU cancels A/C-cut, the FICD solenoid is immediately energized but the A/C compressor is not returned to operation until a specified time has elapsed and engine speed is above 1100 rpm.