Compressor clutch will not engage 1968 DeVille Conv

[cadillacmike68]

Compressor was not engaging, but I found out why.

[cadillacmike68]

Found the issue.

[Highwayman68]

Which was?

[cadillacmike68]

That's TOP Secret.  I could tell, but then I'd have to .....

[cadillacmike68]

OK, it was / is the Vent switch. It is not connecting to shunt voltage from the yellow feed wire to the purple wire that eventually goes to the compressor clutch coil. I jumped the yellow and purple contacts on the harness the clutch engages fine. I can't just leave the harness jumped because that would run the compressor all the time even if the control was in Vent or OFF.

This is just as hokey as the Lo-Auto switch where a spring back strip moves a set of contacts one way or another. It's probably oxidized.

I found one of my spare controls, figures it was the most scraggly one of them all, and took that one's vent switch off to look at it. Yup, push that nylon knob and the spring moves the contacts. I cleaned the contacts a little. Then figured I'd take the one off the control in the car.

I removed the lower dash access panel (under he steering wheel). I could see the two small 1/4 bolts holding it onto the control, but could only get a firm wrench onto one of the bolts. Those bolts are on there good too. So I could not get the vent switch off. I didn't have time to take whole unit out, so I pulled the 3 wire connector and wired a simple rocker switch with vampire clips on the yellow and purple wires to spade connectors and put that switch near the under dash radio. So I when I turn it to Lo Auto, HI, etc., I can just flip that rocker and the compressor will engage.

To repair or replace the vent switch, I'll have to take the entire control out and that' a real PITA, maybe in a week or two.

I'll also have to take down EVERY box in the garage to find those other two control units. Them bad boys cost me $$$$ to have rebuilt.

Cadillac Tim's book which I bought a while back was a GREAT HELP with this.

The Shop Manual merely said "find the cause of no voltage and correct".   

[cadillacmike68]

I think I remember where the other control units are. They are in an old faded white DELCO Aire box. Now I just have to find that box. 

[cadillactim]

Mike

The real pain is reinstalling the control, getting those two mounting screws started. What can help us take a couple of small pieces of cardstock, post card, or similar material and poke a hole in each piece. Next push the screws through the control tabs, then the card material and "screw" the card material on. This will hold the screws in place as you install the control.

No need to remove the card material afterwards, it's not hurting anything.

Tim

[cadillacmike68]

Thanks Tim.

Now I need to replace the heater core too. 

That saga is here:

http://forums.cadillaclasalleclub.org/index.php?topic=157856.0