It's not the control valve, it's the clutch. I can see that the clutch does not even try to engage even with power to the clutch. There are no shims in the system, it is a magnetic clutch and I can tell that the coil is not powered because it won't attract a screwdriver even with power at the connector. There is an intermittent open in the clutch circuit inside the clutch housing!! Please, I'm looking for someone with experience with aftermarket compressors not wild guesses about what may be wrong, I know what the problem is and the quickest path to working air is to replace the whole compressor..
AceEngineer
P.S. Thanks to Effduration for the pertinent information, I'm going to look into it at my local BMW indy wrench.