Contour Enthusiasts Group Archives Forums General Troubleshooting Another A/C Question, However, it is O/T, for my 87 Buick

Ok,

First day I ever take the whole family in this ride and the A/C fails when I leave Grandma's house

So I check and the compressor is not cycling at all. So I think I can rule out a leak in the system. (I had one repaired last year and the compressor cycles on and off quickly.)

So I suspect one of the switches is not working properly.

With the engine running, and the A/C in the ON position, I do NOT have a 12V at either terminal on the compressor clutch. On one terminal I do have a ground (tested with the engine and A/C off).

I then probed the wires that attach to the switch on the dryer (I think that is what it is, the cylinder near the firewall.) And one of the wires had +12V. I then checked a switch closer to the compressor. I don't know if this is the high pressure switch or not, but it goes to one of the lines that is near that little A/C radiator up front.

(Don't you just love my terminology?)

I did have +12V there too. I haven't checked the switches yet to see if they are open or closed, but I suspect at least one of them to be closed.

Now my questions.

1. Am I on the right track? I think so, since I'm looking to engage the compressor.

2. Other than checking these pressure switches, are there any other switches that I've missed.

3. Am I justified to suspect the second switch mentioned (the one NOT on the dryer.) It seems that the switches would progress from the power relay on the firewall, to the compressor.

I believe from the pretty lame diagram in the Haynes repair manual I have, that I have a good relay and good power, as I expect these switches to be part of the path between the +12V source and the compressor clutch.

I don't expect to actually replace one of these switches myself, but would like to have an idea what it is when I take it to my mechanic and describe what I've learned so far.

Thanks for any all suggestions. Suggestions of where to find better wiring diagrams, especially on line will greatly be appreciated.

TB

Now that I look, the relay can still be suspect, as those switches are in line with the relay.

Wonder which relay it is.

TB

Not sure your premise re: no cycling-therefore no leak, is correct.
My a/c didn't work last year, compressor was not cycling, and all it took was a small recharge (no leaks detected).

Ok, fair enough. I would just expect a leaking system to perhaps slowly begin to fail, unless there was a catastrophic sudden failure that caused all the refigerant to leak out.

However, when I had a not so slow leak last fall, the compressor would cycle on, then off, then on until I had it repaired.

Thanks for the reply.

TB

I think you are right.

I jumpered the switch on the dryer and the compressor comes on. Looks like this is a pressure switch.

Got an inexpensive gauge and can of R134a fill kit and when I attached the can of gas to the car, with the jumper in place, the can got cold, and took some into the system.

The pressure gauge that came with the kit said it was in the cool area, but the air never got very cool.

This morning, the compressor once again will not cycle on.

So I suspect I have a leak, again. So it is off to the shop.

TB