Magnetic Clutches

Magnetic clutches have many applications, but as far as a vehicle is concerned, it is used primarily for the air conditioning compressor. The principal will remain the same for different applications. On the front of an air compressor, there is a set of coils wound in a circular fashion and located in a housing. Around the outside circumference of this housing there is a pulley which rides on a set of ball bearings and race that is pressed onto the outside of the magnetic coil housing. The front of this housing has a flat surface facing forward and serves the same purpose as a flywheel. This whole unit rotates around the compressor driven by a belt.

The driveshaft for the compressor protrudes through the center of the flat surface or flywheel. Attached to the driveshaft is a round disc. This disc acts like a clutch in a car. This clutch disc is in very close proximity to the flat bearing surface and held away by the use of metallic springs on the forward side of the clutch disc. When power is applied to the compressor clutch, it causes an electromagnetic field in the coils

behind the clutch disc. This magnetic field attracts the clutch disc to the flat surface of the bearing like a magnet picking up a nail. The magnetic force overcomes the resistance of the springs, and the clutch locks up solid to the flat surface of the bearing and turns the compressor.

If the clutch disc is too far away from the compressor, it will make a metallic scraping noise as it is engaged, indicating that it is slipping. The correction for this is to adjust the disc to be a little closer. If the clutch does not come on, it should be checked for power at the compressor. If there is no power at the compressor, check the fuses and the relay. If there is power at the fuses and relays, there is an open in the magnetic portion of the clutch and the clutch needs to be replaced. If there is a continuous whining noise, the bearing is going bad and needs to be replaced.