I have a 1967 Buick Special, 340-4 with factory A/C. The A/C system is complete and intact. The car is a low mileage (47K) original car. I've had the car for several years and I'm just now getting around to fixing the A/C. I can't get the compressor to kick in when I turn on the air. I can "hard wire" the compressor to 12v and it will kick on so it would seem the compressor and clutch assembly is okay. Any thoughts? thanks.
The supply voltage for the compressor needs to see ground at the other end of the circuit. Is your short wire from the compressor grounded? That's the easy thing to check. After that I would look at fuses and maybe next, the switch at the dash controls.
Some of the older GM ac systems had a "thermal limiter" installed in the wiring near the compressor plug. It is a glorified fuse. It looks like a larger version of the modern plug-in fuses, except that it is black and not see-through. Check it as you would any fuse with an ohmmeter. If it is open, see if you can get another one. I am not sure about availability these days. Worst case - by pass it with a jumper wire.
If the system isn't charged with freon it won't kick in. That keeps the compressor from frying if there is no freon or oil in the system. Bob H.
Now that you've got the compressor to kick in, look at the sight glass on the receiver-dryer and look for bubbles. Bubbles mean that the refrigerant level is low, or it has air and/or moisture in the system. Don't run it a long time that way, because if it is low on refrigerant, the compressor may also be low on oil, and you could trash it. IF you have a thermal limiter, you can find it by following the compressor harness to the inner fender. It has three male spade connectors on it, and if it is popped, it will be obvious- it'll be melted. I believe these only came on cars with a superheat switch. I don't remember the years of application for the thermal limiter, but my dim memory says later than '67. How did you "hard wire" it? In the AC biz, we used to put a jumper in the place of the thermal limiter to get the system charged, then replace the fuse. If you put in a new one, it'll likely blow before the system gets fully charged...then you buy another one, needlessly. I think I still have some in my old AC service machine cabinet, but they are available at most any parts store.
