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wires to ac compressor both have power, HELP
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yimmortal
Novice
Jun 15, 2017, 5:27 PM
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wires to ac compressor both have power, HELP
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ok, I've got a 2002 Hummer H1. that's basically a late 90's chevy diesel 6.5 turbo diesel normal GM ac compressor I have no cold air and the compressor does not engage. I've got the wires that go to the compressor, the brown wire has power, 12v. and the black wire which I assume is ground also has 12v power. how is that possible? I really don't want to take apart the whole dash and trace wires, if I cut the black wire back a few inches and just ground it again is that ok? when I run power from the battery to one lug on the compressor, and a ground to the engine on the other lug, the compressor works and I get cold air is there just a sensor that's not working or something? is it ok to bypass that sensor? realistically what would happen if I did bypass the sensor?
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Sidom
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Jun 15, 2017, 5:49 PM
Post #2 of 10
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Re: wires to ac compressor both have power, HELP
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Sounds like you are just looking at open circuit voltage.... When you checked power was the connector hooked up or disconnected from the clutch?
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yimmortal
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Jun 15, 2017, 5:58 PM
Post #3 of 10
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Re: wires to ac compressor both have power, HELP
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it was disconnected from the clutch when I checked it, ac switched on inside and the truck running.
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Sidom
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Jun 15, 2017, 6:06 PM
Post #4 of 10
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Re: wires to ac compressor both have power, HELP
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Well if it was disconnected then it's not OCV.... Unfortunately my database doesn't have any wiring diagrams for this vehicle, maybe HT's does and he'll post one and we can all take a look at it... The problem with bypassing a system is there are some safeguards built in to keep the compressor coming on if there is a problem...If you bypass something that is a safety that is killing the power due to a problem then you may damage the system.... If it's something as simple as a bad ground or short, then those can be bypassed as long as the problem isn't effecting any other wires in the harness..
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yimmortal
Novice
Jun 15, 2017, 6:30 PM
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Re: wires to ac compressor both have power, HELP
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I'm not sure if I got the picture right, but here is the schematic if the link works on here..... <a href="http://autoforums.carjunky.com/photos/pic/354mbnF1/1185.jpg"><img src="http://autoforums.carjunky.com/photos/pic/354mbnF1/1185.jpg" border="0"></a>
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Sidom
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Jun 15, 2017, 6:54 PM
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Re: wires to ac compressor both have power, HELP
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Nice job on the diagram....Where did you find?... Going off that diagram, it looks like your ground wire has a bad connection and you are probably seeing ocv via the diode.... The ground wire (black) shouldn't be too long, you should be able to trace it down to it's connection and see whats up.... A lot of those would ground to a compressor mounting bolt or some where on the manifold close to the comp....... If you fix that wire your system should work normally
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yimmortal
Novice
Jun 15, 2017, 6:57 PM
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Re: wires to ac compressor both have power, HELP
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yeah, I've got a full manual to fix the truck, 1500ish pages, lol. but I don't understand all the symbols on electrical diagrams so I'm not afraid to ask questions unless I hear different from someone else by morning I'm just gonna ground out the wire... searching for it in a hummer is almost impossible... hopefully you will never have that nightmare to understand what I'm talking about, ha ha thanks :-)
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Sidom
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Jun 15, 2017, 8:05 PM
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Re: wires to ac compressor both have power, HELP
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Yea I've never been a big fan of chasing shorts or opens... Grounds aren't too bad, power wires you definitely want to find out whats going on.... Personally I like to find out what took it out so nothing else gets taken out......But I hear ya those diesels can be a PITA with their harness... Good luck.....I'm sure you'll get it going
(This post was edited by Sidom on Jun 15, 2017, 8:09 PM)
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Hammer Time
Ultimate Carjunky
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Jun 15, 2017, 8:10 PM
Post #9 of 10
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Re: wires to ac compressor both have power, HELP
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If you're reading power on that ground wire with it unplugged from the compressor, you want to be careful about applying ground to that wire. Find out where that power is coming from before you splice a ground to it. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Sidom
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Jun 15, 2017, 8:31 PM
Post #10 of 10
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Re: wires to ac compressor both have power, HELP
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I'm pretty sure he is seeing ocv but it would be a good idea to double check that... With the connector disconnect and the a/c switch turned on,,,, when you are reading power on both terminals......turn the a/c switch off and there should be 0 volts on both terminals.....
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