Hi. I just recently started to troubleshoot some climate control gremlins on my 1987 780 and have a few questions. When I have the ACC set to auto the A/C clutch will not engage (there is always the possibility of low charge). I unhooked the clutch from the harness and hooked it directly up the 12+ on the batterly. Clutch engages, and as near as I can tell the compressor works fine, one of the lines on it gets cold while the other gets hot. I tested resistance on the pressure switch on the drier and came out with appx 90 ohms (this was prior to running the a/c compressor) Is this a normal reading? Is it a simple pressure switch or is it a varistor? If that's not the problem, what other things should I look at? +12 V is going to one lead going into the pressure switch, and the A/C fuse is fine. Thanks in advance