Roland,
When asking questions concerning your car you should tell what it is. I assume you're talking about a Nippondenso AC unit.
If so, why do you have 12.9 volts at the compressor if it is not turned on? This doesn't make sense.

And if the gap is too large the compressor does not have to be replaced. It needs to be removed and put on a bench. There is a nut in the front of the clutch, remove it and the front hub. Under the hub, as it contacts the ridge on the shaft is a spacer that comes in different thicknesses. Find a thinner spacer and your hub is closer. Time consuming but not expensive if DIY.

Tobias MB
C280Sport, 300CE, 400E, 190/5.0