Operation

OPERATION

The A/C compressor clutch components provide the means to engage and disengage the A/C compressor from the engine accessory drive belt. When the electromagnetic A/C clutch field coil is energized, it magnetically draws the clutch plate into contact with the clutch pulley and drives the compressor shaft. When the coil is not energized, the pulley freewheels on the clutch hub bearing, which is part of the pulley.


A zener diode is connected in parallel with the clutch electromagnetic coil. This diode controls the dissipation of voltage induced into the coil windings by the collapsing of the electromagnetic fields that occurs when the compressor clutch is disengaged. The zener diode dissipates this induced voltage by regulating a current path to ground. This arrangement serves to protect other circuits and components from potentially damaging voltage spikes in the vehicle electrical system that might occur if the voltage induced in the clutch coil windings could not be dissipated.


The compressor clutch engagement is controlled by several components: the A/C-heater control in the passenger compartment, the A/C pressure transducer on the liquid line, the evaporator temperature sensor in the HVAC housing for RS models or on the expansion valve for RG models, the powertrain control module (PCM) in the engine compartment, and the compressor clutch relay in the integrated power module (IPM). The PCM may delay compressor clutch engagement for up to thirty seconds.


The A/C compressor clutch components cannot be repaired and, if faulty or damaged, they must be replaced.