1987 190D 2.5 Non turbo with issues with the AC.
It comes on for a few seconds when I start the car, then it shuts off.
I Charged the AC with an AC machine a few months ago. So I am very confident that it is not the refrigerant, because it held a very good vacuum and when the AC does work, it is COLD.

I can wire the AC compressor directly to 12v, and the compressor will stay on, so I know the AC is working, but it seems that something keeps sending a signal to shut off the compressor.
I also found that I can unplug the relay (behind the battery) and plug it back in, and the AC will run for a few seconds, then shut off again. I replace the Relay with a known good one, but the symptoms are the same.
Also, the PO bypassed the switch on the low-side of the dryer many years ago.

I have searched this forum for similar issues, and found this one- A/C diesel problem

Before I tear into the dash, I was wondering if there are any other things I can check that would be simpler/easier.