My a/c shuts off after about 2 seconds after turning on engine. Noticed that the ac was cycling off randomly and the engine temp was only at about 80C. Then the ac would cycle back on randomly and stay on for a while driving then turn off. Got how and did a few tests: refrigerant level is fine, low pressure/high pressure switch is working, high temp switch is working, fan is working, compressor is compressing properly. I ran straight 12v to the compressor to engage clutch with engine off and it did engage. So the compressor is working, but there is some minor hiccup I'm missing because the problem is intermittent and random. Any suggestions?

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1990 190E 3.0L