Pacifica V6-3.8L VIN L (2005)
Compressor Clutch Coil: Description and Operation
A/C Compressor Clutch
The A/C compressor clutch assembly consists of a stationary electromagnetic A/C clutch field coil with a zener diode, a pulley bearing and pulley
assembly, and a clutch plate. These components provide the means to engage and disengage the A/C compressor from the engine accessory drive belt.
The A/C clutch field coil and the pulley bearing and pulley assembly are both retained on the nose of the A/C compressor with snap rings. The clutch
plate is splined to the compressor shaft and secured with a bolt.
The A/C compressor clutch components provide the means to engage and disengage the compressor from the engine serpentine 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 A/C clutch field 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 A/C compressor clutch engagement is controlled by several components: the heater-A/C controls in the passenger compartment, the A/C pressure
transducer on the liquid line, the evaporator temperature sensor on the A/C expansion valve, the powertrain control module (PCM) in the engine
compartment, and the A/C compressor clutch relay in the integrated power module (IPM). The PCM may delay compressor clutch engagement for up to
thirty seconds.