It appears that my compressor is locked up, but I wanted to ask if there was anything mechanical in the clutch that would cause it to lock up and not turn the compressor. I believe I still have proper line pressure as the clutch will try to engage when commanded, but it will not grab the pulley and turn -not even turn a little bit. It just slips. After a few seconds it disengages and will not reactivate. I then get code 67 (no change in line pressure after 10 secs) when this happens. I do not get a code 66 (pressure too low or high). Reset the PCM, and can repeat the whole process.
Is it possible for the compressor to lock up but still have a leak tight system? I'm guessing it is, unless the clutch has some kind of mechanical lock that activates when it is worn too much.
This is the original compressor/clutch. I'm at 189K now. Can't complain if it is time for a replacement. Any thoughts appreciated.

94 Z28 converted to M6 at 145K

 

Could be a pressure switch gone bad... If you think you need a new A/C clutch I have one new AC Delco in the box... email me if you need it