OK, I'll test the following things as some of you suggested and add to my list of things I was already going to try, then report back to you in the thread.

1. Test resistance of Evap Temp switch at ambient temp (with system off) and when running cold.

2. Test resistance of Cabin temp sensor at ambient temp. Try to see if it varies with temperature. If not, try swapping in different resistor values to see if I can get the temp mix to change. Book says just a few hundred ohms, I have several resistors in that range handy to test with.

3. Check to see if the compressor still runs when the temp wheel is backed off the full-on detent position.

4a. Test monovalve plunger function by removing plug while system is on. Hey that won't overload the monovalve control circuit in the pushbutton control will it? That monovalve pulls a lot of juice. I heard someone say just fooling with the aux pump power connection can blow circuit board traces in the control unit.

4b. Test power output to monovalve when in cooling and heating modes and see if it's within specs. Test disconnected monovalve for shorts/opens. Scream loudly so the all neighbors can hear if I have to buy a new one right after springing $40 for a new plunger.

Additional question: extra credit to help out a poor pre-med student
Anyone know of any way to rebuild a monovalve coil? Or do I have to stand up and pay for a new one just to get the darned coil? My #$%^&! plunger's brand new. I'd be great working for Mr. Scott on the Enterprise, no warp drive parts stores in the neutral zone. "I'll rig something up but I dunno if it'll hold for long, Captain". The mythical legendary engineer, that guy could fix anything with nothing, anywhere, in no time. It always seemed like it was in the nick of time. Oh well, that's the difference between fiction and fact.

Regards,

Theo

klakka klakka klakka klakka...Arf arf arf...
The darned dog always knows when Theo's home!