RAM 1500 Van V8-5.2L CNG VIN T (1999)
Compressor Clutch Relay: Description and Operation
A/C Compressor Clutch Relay-PCM Output
AIR CONDITIONING (A/C) CLUTCH RELAY - PCM OUTPUT
Power Distribution Center (PDC) Location
The A/C relay is located in the Power Distribution Center (PDC). The PDC is located in the engine compartment next to the battery. Refer to label
on PDC cover for relay location.
The Powertrain Control Module (PCM) activates the A/C compressor through the A/C clutch relay. The PCM regulates A/C compressor operation
by switching the ground circuit for the A/C clutch relay on and off.
When the PCM receives a request for A/C, it will adjust idle air control (IAC) motor position. This is done to increase idle speed. The PCM will
then activate the A/C clutch through the A/C clutch relay. The PCM adjusts IAC stepper motor position to compensate for increased engine load
from the A/C compressor.
By switching the ground path for the relay on and off, the PCM is able to cycle the A/C compressor clutch. This is based on changes in engine
operating conditions. If, during A/C operation, the PCM senses low idle speeds or a wide open throttle condition, it will de-energize the relay. This
prevents A/C clutch engagement. The relay will remain de-energized until the idle speed increases or the wide open throttle condition exceeds 15
seconds or no longer exists. The PCM will also de-energize the relay if coolant temperature exceeds 125°C (257°F) or low or high system
pressure exists.
