A/C electrical?

[RBStratman]

My A/C has cut out. It's getting hot here in PA. Last year I replaced the compressor with a re-built one. It worked most of the summer and then died until I fiddled with the wires by just jiggling them and it worked again...until this spring. The charge is holding and is fully charged. The fuses are fine. The wiring is showing no kinks or breaks in the engine compartment anyway. The compressor would only kick on when I revved the engine after driving a while. I recently replaced the alternator as well (last week). Before I replaced the alternator I was wondering if the compressor was getting enough voltage to kick on normally without the revving and was hoping that when the alternator went dead, that replacing it would cure my compressor problem as well but it didn't.
Now I can't get it to come on no matter how much revving I give the engine and can't seem to find the problem. The Haynes book says that replacing the AC/Heater switch panel is the last resort. Have I reached my last resort yet? I have a 98 Lumina LTZ with the 3.8.
I'm really heating up here in PA.

[jeffcoslacker]

Check the pigtail to the compressor for 12v with the air on. If you have power but no operation, you've got a faulty clutch.

If you are certain it has a good charge (I'm wondering how you can tell if it doesn't work, please advise) you could try a jumper in the low pressure switch and see if that will get it to engage. If it cools good like that, the low pressure switch is faulty.

I tell you what, on my own stuff, I'll run 12v straight to the compressor and force it to run before I'll drive around without A/C.

With a test light, make sure the compressor pigtail has a good ground as well.

[RBStratman]

Thanks jeffcoslacker. I'll try looking for 12v at the compressor. I checked the charge when I did get it to work a couple of weeks ago and that's how I'm pretty sure that's not the problem. However, you never know and if I can get the compressor to run, I will double check the pressure again.
If it's the low pressure switch it shouldn't be a problem to replace, but if I have to run 12v direct, I certainly will.
Judging from the way it ran when I did get it to run, the clutch seemed smooth.
Thanks again.
Brian

[jeffcoslacker]

I've had a couple of cars that the A/C wouldn't work right, and I ended up hotwiring the clutch to get it to work. Just keep in mind if you do run it like that, you have eliminated all fail-safes to prevent system damage, so keep that in mind. Like if you had a blockage or a low charge, it'd run anyway, and destroy the compressor and shoot debris into the system.

I don't want you to hate me for suggesting it.

I had one I did for a neighbor 3 years ago, I did the quick and dirty R134a retrofit, where you just vac the system and shoot in the conditioner oil and the new stuff, and it worked good, but when on the highway it would kick in and out, warm for 20 seconds then real cool, over and over. I figured the pressure switches were probably not "tuned" right for the higher pressure of the 134a, so I just gave her a hotshot switch on the dash to power the compressor and override the system on the highway. It's still working fine. I would have fixed it the right way, but she didn't have any money to spend fixing anything else. It was one of those "If it works till the end of the summer, I'm happy" kind of deals. 3 seasons, still going strong.