1990 300E a/c compressor/clutch gremlin?

[Benz Mondi]

What do I need to do to engage the a/c clutch while this new compressor is on my bench?

Genesis: Suddenly, my a/c compressor won't engage again, In my previous post, when I pushed the a/c button on my climate control, the #7 fuse would blow. I thought I had narrowed it down (by disconnecting various items in the system) to a bad MAS. I replaced it with a used one and all worked again.

Now, though the #7 fuse doesn't blow, the clutch wont' engage. I'm on my 3rd MAS and 2nd OVP and still nothing.

I even have a new (rebuilt) compressor on hand (ordered for my SL) to use as a test bed. Unlike other compressor clutches on my other non-MBZ cars, I could just apply 12v to the clutch plug and get the clutch to move in-ward to engage. I can't seem to get even the clutch on the new one to engage after applying 12v to 2 of the 3 poles in the socket, in any combination.

Any ideas?

Thanks.