Cherokee 2WD L4-150 2.5L VIN P MFI (1991)
A/C Signal: Description and Operation
Air Conditioning Request Signal
The air conditioning information pertains only to those vehicles with factory installed and aftermarket Jeep air conditioning units. Factory installed air
conditioning units are not available for YJ vehicles with 2.5L engines.
Once the air conditioning has been selected by the driver, the evaporator provides an input signal to the engine controller, if the evaporator temperature
is within a specified range, this signal is referred to as the A/C request signal. Once the engine controller receives this input, it applies the ground to the
A/C clutch relay so that the A/C clutch can be ENERGIZED, and it sends output signals to the Automatic Idle Speed (AIS) motor to raise the idle speed
to a predetermined rpm to compensate for the additional load placed upon the engine.
If the evaporator is not at the proper temperature, the evaporator switch will open and the engine controller will not receive the A/C request signal. If the
engine controller does not receive the A/C request signal, the engine controller will then remove the ground from the A/C relay, DE-ENERGIZING the
A/C compressor clutch.
