Compressor Clutch: Service and Repair

The compressor clutch on the Nippondenso compressor is replaceable.

If the compressor is inoperative, there are several possible causes. The power supply or ground may not be adequate to operate the coil, the clutch may be faulty; or the belt may be slipping. If the belt is slipping, there are several possible causes:
- Belt tension too low (or belt condition poor).
- Oil on the clutch surface (a leak from the compressor).
- The compressor could be on the verge of failure, and is operating intermittently.
- Very high or very low high-side pressure (this opens the pressure switch).

Belt Tension Gauge II 5 021:

With some designs, the belt tension can be adjusted manually and checked using a BMW special tool; on other designs it is adjusted automatically by a spring-loaded tensioner.

Be sure to check the belt for cracks, tension, and oil contamination. A leaking compressor can spill oil on the belt, causing slippage. However; a small amount of oil seepage at the compressor seal is normal; the compressor does not need to be replaced if only a small amount of oil or dirt is present.

V12 engines produced through the 1992 Model Year have a lock sensor control module, which can cut off power to the compressor clutch.

If compressor noise is present with the clutch disengaged, the bearing in the clutch is the problem.

If compressor noise is present with the clutch engaged, the compressor internal parts are the problem.


NOTE: a click when battery voltage is applied does not always mean the compressor clutch is good; it only means battery voltage is available to the coil.


To replace the compressor clutch, remove the protective plate underneath the compressor and remove the drive belt.







Grip the drive plate with special tool 64 5 090 (for the Nippondenso compressor) or special tool 64 5 020 (for the Seiko Seiki), unfasten the screw, and remove the drive plate.

Pull off the belt pulley/bearing assembly using a standard three-claw extractor tool. Apply the pulling claws only at the joint between the solenoid coil and the belt pulley - otherwise the belt pulley will be damaged.

Spread and remove the circlip. Unfasten the retaining screw, disconnect the connector, and remove the solenoid coil.

When installing the new clutch, note the position of the circlip: the beveled side must point outward.

Make sure the clearance between the drive plate and the pulley is correct (0.5 to 0.8 mm). Shim the drive plate with washers, if necessary.