be absolutely certain that the clutch is disengaged, and the pulley will just freewheel, and not turn the internals of the compressor. You'll probably still want to make sure that the internals have a light coat of lubricant, and that the ports have plugs on them. I can't provide any logical reason for the light coat lube and port caps, except that my gut says that it'd be better than not :) But as long as the clutch is disengaged, I can't think of any harm you could do to the compressor.