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wires to ac compressor both have power, HELP


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yimmortal
New User

Jun 15, 2017, 5:27 PM

Post #1 of 10 (586 views)
wires to ac compressor both have power, HELP Sign In

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?


Sidom
Veteran / Moderator
Sidom profile image

Jun 15, 2017, 5:49 PM

Post #2 of 10 (582 views)
Re: wires to ac compressor both have power, HELP Sign In

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
New User

Jun 15, 2017, 5:58 PM

Post #3 of 10 (575 views)
Re: wires to ac compressor both have power, HELP Sign In

it was disconnected from the clutch when I checked it, ac switched on inside and the truck running.


Sidom
Veteran / Moderator
Sidom profile image

Jun 15, 2017, 6:06 PM

Post #4 of 10 (573 views)
Re: wires to ac compressor both have power, HELP Sign In

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
New User

Jun 15, 2017, 6:30 PM

Post #5 of 10 (563 views)
Re: wires to ac compressor both have power, HELP Sign In

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>


Sidom
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Sidom profile image

Jun 15, 2017, 6:54 PM

Post #6 of 10 (553 views)
Re: wires to ac compressor both have power, HELP Sign In

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
New User

Jun 15, 2017, 6:57 PM

Post #7 of 10 (547 views)
Re: wires to ac compressor both have power, HELP Sign In

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 :-)


Sidom
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Sidom profile image

Jun 15, 2017, 8:05 PM

Post #8 of 10 (537 views)
Re: wires to ac compressor both have power, HELP Sign In

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






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(This post was edited by Sidom on Jun 15, 2017, 8:09 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 15, 2017, 8:10 PM

Post #9 of 10 (523 views)
Re: wires to ac compressor both have power, HELP Sign In

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.



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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.



Sidom
Veteran / Moderator
Sidom profile image

Jun 15, 2017, 8:31 PM

Post #10 of 10 (515 views)
Re: wires to ac compressor both have power, HELP Sign In

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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