QuestionQUESTION: The compressor for my Olds does not come on when I turn on the a/c. My brother, an ASE mechanic, jumped the low pressure switch and the compressor would still not come on. He was just down visitng from NY and didn't have any of his gauges with him, so he was just doing a quick check on it fo me. He said he thought he recalled that there might be another fuse somewhere that might be at fault. The fuse under the dash was OK. A few years ago I had a lot of work done on it and it was fine. My mechanic said that about the only thing that wasn't replaced was the low pressure switch, but jumping it didn't do anything. Before I toss in the towel and take back to my mechanic, is there anything else I can check while the car is in my driveway and maybe save a few bucks?
ANSWER: Jim,
there should be an A/C fuse in the dash. This is the one basically controlling the control head itself. But there should also be another one that is labeled A/C clutch. Typically this is located in the box that contains your relays. If you know where that is... good... because that is the next place I want you to start checking. In that box there is a relay for your A/C clutch. This is the first step after the fuse that sends power through your low pressure switch, high pressure switch and clutch itself.
With your low press. switch jumped...
Locate and unplug the relay that is labeled for your clutch. Run a jumper wire across the contact terminals in the plug. You may have to try a couple combinations unless your relay has a diagram on it indicating which plug is which. You want the contact power input to jump to the contact power out. If it is labeled it will have a coil in and a coil out, this is indicated by a picture of what looks like a spring. We are not using these for this check. Again if it is labeled, it should have one dot on one side with a number and across from that single dot there should be 2 dots. One is connected to the dot across with a line. You want to jump the connectors for the single dot and the dot that is not touching the line. I really wish that allexperts.com let us draw or add pictures to these responses, because I have a feeling I just confused you. But if you jump them and you hear the clutch engage (key in run position, engine can be off, and the A/C switch on), plug your low pressure switch back in. Did your clutch disengage? If so... check your refrigerant charge. If it is good, repplace your low pressure switch.
If the clutch stayed engaged... Plug your relay back in. If it isn't engaging now... your relay needs to be replaced. Chances are your coil inside the relay has burnt and is not allowing the contacts to "flip"
I know this is not the most user friendly answer, and if you need me to try re-wording it, let me know. But I hope I was able to help just a bit. If I can do anything more, do not hesitate to ask. Thank you for the question and good luck.
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QUESTION: David,
I'm driving cool as a cucumber now! Thanks!
OK, here's what I did. I located the "Maxi-fuse and relay center" which was on the firewall under a black, plastic cover. I first checked a very large fuse which was OK. Then I saw the relays. Unfortunately, they were not marked. I called my mechanic, who was kind enough to help me locate which relay was for the a/c clutch. We verified this by the color of wires coming out the back of the relay. What was odd was there were only 4 relays on the "rail" that holds them all. There were 2 other relays that were just lying up near the accumulator. One of them was the a/c clutch relay. Apparently, just by moving it around, it started working the a/c clutch. I'm told that relays are very finicky and sometimes work intermittently. Just to be safe, I located a relay for just $7.33 at a local parts store and replaced it anyway.
As to your instructions: I did see a diagram of sorts on the side of the relay. I never did get around to jumping it as it wasn't necessary after it started working. I figured for just $7.33 I'd just go ahead and replace the relay. After I removed the relay, there were 4 receptacles in the plug. Perhaps the easier way to describe what I needed to jump would have been to say to jump the receptacles that were top-bottom or left-right. I think I understand that the relay receives a low amp current that closes the switch to allow the higher amp current to flow. I figured that 2 of the receptacles were for the low and the other 2 were for the high, and it was the high that I needed to jump. In any event, would it have made a difference if I had jumped them both? I know you were frustrated that you couldn't draw a picture, and I may have described it incorrectly myself.
Anyway, you had me going in the right direction, and with the heat index here today well over 100º, I'm very glad to have it working.
Thanks again.
AnswerJim,
I am glad that I could assist you. I'll keep that in mind when describing how to jump the relays. But with that, it wouldn't have made a difference if you jumped them both, as long as you didn't end up jumping the hot to hot and the not to not. Then it would have blown the fuse and gotten both of us confused.
But I am very glad to hear you are running cool again. And without any major events ($$$) being involved.
If you found my replies at all helpful, please remember to rate my replies. And if I can be of any assistance now or in the future, do not hesitate to ask. Thanks again and good luck in everything.
