Ok so I have a 78 240d I got recently. It has been converted to r124 based on the connections. It does have pressure but a/c compressor does not come on. It has a two terminal phillips screw block on the back(I assume this is the low pressure switch). One terminal is running from this to behind the pulley(I assume this is clutch selenoid). Then it did not have anything going to the other connector, I was hoping this was the only problem but it's not. I ran 12 volts directly to the wire going to the clutch and it does not engage.

So is there a selenoid that can be replaced? What's the next step at this point? The center part turns by hand so it's not locked up....

the clutch is done, replace it. good luck, chuck.