Comanche 4WD L4-150 2.5L VIN P MFI (1991)
Compressor Clutch Relay: Description and Operation
Power Distribution Center
The engine controller uses this relay to control the air conditioning compressor clutch. When air conditioning is turned on in the vehicle, the A/C
evaporator switch will send a signal to the engine controller and it will send a signal to the idle speed stepper motor and adjusting it to compensate for
the increased engine load. After the idle speed increases, then the A/C compressor clutch relay will be ENERGIZED by the engine controller and
voltage will be allowed to flow to the A/C compressor clutch (ENERGIZING the A/C compressor clutch). This relay is located next to the coolant
recovery bottle.
The engine controller is able to cycle the A/C clutch relay for different engine operating conditions by switching its ground ON and OFF. If the engine
controller senses a wide open throttle or low idle speed condition, via the throttle position sensor, it will remove the ground to the A/C clutch relay,
de-energizing the relay, which will prevent A/C clutch engagement. The relay will continue to be DE-ENERGIZED until the idle speed increases or
until the wide open throttle condition no longer exists or exceeds 15 seconds. The engine controller will also DE-ENERGIZE the relay if the coolant
temperature exceeds 125~C (257~F).
