Compressor Clutch: Description and Operation

A/C Compressor Clutch - Typical:

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.

On models equipped with the 2.0L and 2.4L Turbo engines, both the A/C clutch field coil and the pulley bearing and pulley assembly are retained on the nose of the compressor with snap rings. On models equipped with the 2.4L naturally aspirated and 2.7L engines, the pulley bearing and pulley assembly are retained on the nose of the compressor with a snap ring and the A/C clutch field coil is pressed fit to the nose of the compressor. On all models, the clutch plate is keyed or splined to the compressor shaft, and secured with a retainer.

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 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.
- A/C-heater control in the passenger compartment
- A/C pressure transducer on the A/C discharge line
- Powertrain control module (PCM) in the engine compartment
- A/C clutch relay in the power distribution center (PDC)
- Models equipped the 2.0L and 2.4L Turbo engine also use a thermal limiter switch mounted to the A/C compressor to disengage the clutch if compressor surface temperatures become excessive.
The A/C compressor clutch components cannot be repaired and, if faulty or damaged, they must be replaced.