Durango 4WD V8-5.9L VIN Z (1998)
A/C Signal: Description and Operation
NOTE: The A/C control system information applies to factory installed air conditioning units.
A/C SELECT SIGNAL:
When the A/C switch is in the ON position, an input signal is sent to the powertrain control module (PCM). The signal informs the PCM that the
A/C has been selected. The PCM adjusts idle speed to a pre-programmed rpm through the idle air control (IAC) motor to compensate for increased
engine load.
A/C REQUEST SIGNAL:
Once A/C has been selected, the powertrain control module (PCM) receives the A/C request signal from the clutch cycling pressure switch. The
input indicates that the evaporator pressure is in the proper range for A/C application. The PCM uses this input to cycle the A/C compressor clutch
(through the A/C relay). It will also determine the correct engine idle speed through the idle air control (IAC) motor position.
If the A/C low-pressure switch or high-pressure switch opens (indicating a low or high refrigerant pressure), the PCM will not receive an A/C
request signal. The PCM will then remove the ground from the A/C relay This will deactivate the A/C compressor clutch.
If the switch opens, (indicating that evaporator is not in proper pressure range), the PCM will not receive the A/C request signal. The PCM will
then remove the ground from the A/C relay, deactivating the A/C compressor clutch.
