Originally Posted by pettyfog

Thanks for the replies, yes it is the automatic control. And yes, unlike earlier vintage, switcheS all feed the ECM and it controls compressor
Les, that's a good idea. I'll get one, replaced it about 8 years ago and it may be time. Was pretty sure I tested that already but I am an old fart.
BTW, the input impedance on ECM is relatively high compared to a relay and that's how oil pollution could screw it up.
SIDENOTE for posterity: Another cause of this which I have seen twice in last 5 years is excessive clutchplate clearance.. Test for that is to tap the flex plate with screwdriver handle. If clutch engages, adjust shimming. I checked that early on and that ain't it.