The clutch in a compressor uses far more current than can be accommodated through the on-dash A/C switch. It is for that reason, as noted above, that a relay is used. When power from the driver’s control reaches the compressor clutch relay, it actuates the relay’s internal switch. A much greater current then is delivered to the compressor clutch, the clutch engages the rotation of the belt with the compressor, and the compressor starts to function.
Friday, 14 February 2014
Compressor Clutch
Because the fan belt intended to rotate the compressor is permanently attached to the crank, either directly or indirectly, it is always spinning when the engine is running. The A/C compressor does not need to work constantly; it is only needed when the air conditioning is switched on. For this reason, a device is needed that engages the compressor to the rotation of the belt when required and disengages the compressor from the rotation of the belt when not required. This is the function of the clutch, which is an electromagnetic device permanently attached to the fan belt. When it is not energized, the clutch is not in contact with the drive of the compressor, so it spins without spinning the compressor. When energized, the clutch moves toward the compressor until it contacts the drive, and the drive thus begins to rotate. When power is disconnected from the clutch, it retracts away from the A/C compressor, which ceases to rotate.
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