Replaced ac compressor, charged ac, no power to compressor

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troywalker83
Posts: 2
Joined: Sat Sep 10, 2016 6:33 pm

Replaced ac compressor, charged ac, no power to compressor

Postby troywalker83 » Sat Sep 10, 2016 6:50 pm

I've got a 07 town and country giving me ac problems... it came to my shop with a noisy compressor. Driver said it had been making noise for a while and finally got so hot it almost caught fire..... replaced compressor, filled with oil and freon. Still no power to compressor. Relay and fuse good. Pulled relay and have power in 2 terminals.. jumped power to compressor and turns on and blows cold.... could it be a bad pressure switch? Scanned ac system with scanner, no codes. Looking at the wiring diagram I have, not sure if the other terminal at relay should have power... I've got 2 with power and 1 going to compressor. 4 total.
GM Tech
Posts: 145
Joined: Fri Apr 22, 2016 7:22 am

Re: Replaced ac compressor, charged ac, no power to compressor

Postby GM Tech » Sat Sep 10, 2016 7:32 pm

The ECM throws a negative to the relay coil to engage the relay and thus the compressor....so your issue is upstream- as in an ECM input- no codes get set when this happens, either the low temp thermistor is bad, or the high side pressure transducer is amiss- look for 3 wires at the transducer- one is ground, one is probably 5 volts and the other is return or reference..
troywalker83
Posts: 2
Joined: Sat Sep 10, 2016 6:33 pm

Re: Replaced ac compressor, charged ac, no power to compressor

Postby troywalker83 » Sun Sep 11, 2016 7:13 am

I've got the 5v reference. Ground. The signal voltage is 1.86. Says it should be between .451-4.519
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Jag987
Posts: 49
Joined: Thu Apr 21, 2016 9:16 pm

Re: Replaced ac compressor, charged ac, no power to compressor

Postby Jag987 » Mon Sep 12, 2016 9:56 pm

I replaced a compressor on a caravan once that had be removed and a bypass put in a couple of years before. Same thing, it would not come on. Fuse/relay were good, wiring all liked good, just no power to the compressor. I would have to look it up again, but there is a way to run the control head through a self diagnostic check. I did this two or three times then it started working properly. Might be worth a try.
I bought a can of freon at supermart. It had dye, oil, and stop leak in it. It also came with a hose and a gauge. Now I'm an ac professional!!!

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