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A look at the compressor clutch

The compressor is usually belt-driven by the engine crankshaft, and engages through an electromagnetic clutch. When the air conditioning is off and the engine is running, the compressor pulley is freewheeling. When the system is activated, electrical current passes through an electromagnetic coil mounted behind the pulley. A clutch plate mounted on the front of the pulley is magnetically pulled against the turning pulley. This locks the pulley and plate together. Since the plate is splined to the compressor drive shaft, the compressor operates when the pulley turns.
Many thanks to MACS member Compressorworks for the photo used in this post.
When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.
You can E-mail us at or visit to find a Mobile Air Conditioning Society repair shop in your area. Visit to find out more about your car’s mobile A/C and engine cooling system.

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