Adjusting the clutch air gap on the Saab 9000 air conditioning compressor


On Saab 9000s equipped with air conditioning (and/or climate control) the air conditioning compressor is driven by an electromagnetic clutch. In normal operation, the clutch cycles on and off regularly. Over time, however, the clutch wears and the air gap between the clutch and the driven plate increases to the point where, under certain circumstances, the magnetic coil can no longer pull the plate against the clutch. The first sign of failure is that the air conditioning stops blowing cold when the under-bonnet temperature rises significantly. This is because the high temperature causes the coil resistance to rise, reducing the available current and consequently the strength of the magnetic field.

I took the car to an air conditioning technician, thinking there was a problem with the refrigerant. After an unsuccessful attempt, he finally verified that there was voltage to the clutch and proved the cause of the problem by tapping the clutch driven plate with a hammer with the engine running, whereupon the clutch engaged and the compressor started running. I watched him fix it using the following procedure. Since I have seen a number of reports of this problem, I felt it worthwhile to dismantle the clutch again in order to document the procedure for other Saab owners.

This procedure was performed on the Seiko compressor on my '96 Aero. Some other models are fitted with a Sanden compressor. While the same principles apply to the Sanden compressor, certain details may vary. However, after lengthy discussion with other 9000 owners, it appears that this problem is almost exclusively confined to the Seiko compressor.

Time required

Around 10 minutes.

Tools required

  • 5mm Allen key or hexagon bit.
  • Feeler gauge
  • Screwdriver to lock the driven plate.
  • Thread locking compound.


  1. Locate the compressor clutch as shown below.

  2. Using a feeler gauge, measure the air gap. It should be between 0.4mm and 0.8mm (0.016" and 0.031") for the Sanden compressor and between 0.3mm and 0.6mm (0.012" and 0.024") for the Seiko compressor. If it is too large, adjust it by following the procedure below.

  3. Using a 5mm Allen key or hexagon bit, unscrew the central retaining screw. Use a screwdriver to stop the driven plate (and compressor shaft) from turning. Remove the screw and its washer.

  4. Carefully remove the clutch driven plate, taking great care not to lose the shims underneath - on my car, the shim was stuck to the plate and fell into the engine bay as I withdrew the plate. There was only one shim, but since the gap on my clutch had already been reduced, I know that at least one shim had already been removed. The driven plate and shim can be seen below. The wear on the plate after almost 150,000 miles is quite apparent.

  5. Remove one or more shims to achieve the required gap. Refit the remaining shim(s) onto the compressor shaft. On the Seiko compressor, each shim is approximately 0.5mm thick.

  6. Refit the driven plate. I found that the retaining screw had had thread locking compound applied, so I applied fresh threadlock. Refit the screw and washer and, using the screwdriver to stop the driven plate from turning, tighten the screw. I don't have a torque figure.

  7. Re-check that the air gap is now within specification.