A/C: Rebuilt Nippon Denso compressor.
 

Just completed reassembling my 10P15C A/C compressor from my 1987 911. All new seals including case sections, shaft, and manifolds. All appears fine except the spacing between the clutch drive plate and pulley is now just too close with some friction that turns the drive shaft slowly with the clutch turned off. The pulley ran free before disassembling this compressor. Clutch engages properly when switched on. The shaft seal was carefully installed ensuring the two "flats" mated correctly with the shaft "flats, then the seal slipped down into its designed resting place. Both small washer shims were also properly installed. Any ideas?

You need an air gap of .015 to .030"

Typically there are shim washers between the comp shaft 'step' and the underside of the front hub, sometimes they get lost.

We'll assume when you put the pulley back on the nose it sets down to the bottom
and the snap ring in completely inside of the groove on the nose.

Remove the front hub. Check to see if you have shim washers on the shaft step,
and check inside the mating hub's bore.
Measuring the ID of the shaft and ID of the front hub bore. You'll need some small flat washers (if you have not started looking around your work area where they dropped out) that work with these dimensions.

Put the front hub back on.

Get 2 feeler gauges, one .015" and one .030". Imagine the hub face as 3 pieces of pie, maybe pizza with sausage, if your a vegun, maybe kale. Go around the hub and use the .015" feeler and insert between the hub and pulley at each 120 degree mark. The .015" should go in, that is your "go" gauge. Repeat the process with the .030" feeler, it should not go in, that is your "no-go" gauge.

Put shim washers on the shaft step and repeat the process above.

Thanks kuehl, I will report back.

The compressor will have very little resistance to being turned ever so slowly.

You may have a few high spots on the (new?) clutch surfaces that need a little "wear" time.

Very difficult to find these size spacer washers, 8mm inside dam. and 12.5 mm outside diam, with thickness from 0.5mm and up. Where can they be sourced?

lol

Found two correct diameters washers but made of aluminum, thus "squash" washers! Installed them and tightened the shaft nut enough to leave a .018 gap. Thus a temporary fix until I can source steel washer. Clutch is operating correctly. Thanks for your help.