I've had this ac issue for a while now. I originally thought it was air flow. If I'm sitting at idle the ac blows ok cool air, maybe 60° - 65°. Now if I increase the rpm to about 2000 while sitting, it blows colder and I get down to about 40°, but I'm running electric fans so the increase in rpm doesn't bring in anymore air, it just speeds up the resolutions of the compressor. I had to bypass the climate control button because it would not trigger the ac to turn on. There is no power getting to the compressor from the plug, so I wired it to turn on when I turn on the low speed fan or high speed fan. So there is no speed sensor. Does this sound like it's a speed sensor issue or does it sound like the compressor itself is bad. The compressor is a used one because when I had the issue of the ac not coming on with the climate control, I thought the compressor failed so I got a used one then I figured out the latter issue after the fact. Thoughts please. Thanks.

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1990 190E 3.0L