A/C compressor clutch not engaging

MATT CRAWFORD

MEMBER
2003 CHEVROLET SILVERADO
6.0L
V8
2WD
AUTOMATIC
81,000 MILES

So I was cruising down the highway going 60 when I noticed my A/C quit blowing cold air. It was just the warm air from outside. I didn't hear any belt squealing or the compressor grenading itself, so I'm under the impression something caused my compressor to simply turn off, and now it won't come back on. I've tested the 10A fuse and the relay, both of which were good. I've replaced both the high and low pressure switches and tested for voltage at their plugs. Both are good. I tested for power at the plug for the compressor and found that it had no power, it had a good ground though. So I used a jumper wire and hooked it up to the fuse and ran it directly to the plug for the compressor. So I had power going directly to the compressor, yet it still wouldn't come on. I tried to recharge the system with the diy can that hooks to the low pressure port but the system wouldn't accept the charge. So now I'm stumped. My only other guesses to fix this issue are to either evac the whole system and recharge it and hope it works, or the clutch on the compressor is bad. If anyone has ran into these same issues and found a solution please let me know!

Sunday, August 9th, 2020 AT 5:15 PM

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Just to confirm, you had no power at the compressor and when you jumped 12 volts to the compressor, it still did not come on? If that is the case, we are missing something with that.

Take a look at this wiring diagram. You should have power on the green wire at the compressor when you jump the relay for pin 30 to 87. So if you remove the relay and jump those two pins the compressor should come on.

If you have no power and when you give it power and it doesn't come on then we are not doing one of the two correctly. If you are then I get your confusion. Maybe get some pictures or a video of how you are testing for power at the compressor with the engine on and A/C on. Then when you are jumping power as well.

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Basically the way this works is if you turn the AC on, the HVAC module should have the low pressure circuit grounded. If it does then it sends a signal to the PCM. If the PCM gets proper signal from the pressure sensor and signal from the HVAC control module, it grounds the relay and the compressor kicks on. Then it will cycle the compressor based on the pressure sensor reading.

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Friday, April 30th, 2021 AT 4:03 PM

MATT CRAWFORD

MEMBER
6 POSTS

To answer your question. No, I did not have power coming from the factory green wire going to the compressor. So when I jumped it, I just took some loose wire I had and stripped both ends of it, then put one end into the fuse slot. I put the fuse back into the same slot so power would run from the fuse into the jumper wire. Down at the compressor, I stripped a portion of the green wire before the plug and wrapped the other end of my jumper wire around that stripped portion. I tested for voltage coming out of that plug and it was reading 12v. So I plugged it back into the compressor and turned the ac on. Yet the compressor still would not engage. Hopefully I clarified what I did a little better.

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Friday, April 30th, 2021 AT 4:03 PM

KASEKENNY

MECHANIC
18,907 POSTS

You did clarify that. Thanks.

The only issue with doing it this way is there are a number of places that we can loose the 12 volts so we could condemn the compressor incorrectly. If you jump the relay, that is more definitive just because you are using all the existing wiring.

At this point, if you have 12 volts down at the compressor and it still did not come on, it sounds like you need a compressor.

https://www.2carpros.com/articles/replace-air-conditioner-compressor

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Friday, April 30th, 2021 AT 4:03 PM