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Old 07-14-2013, 03:35 PM   #1
1985GMC
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Red 12v wire?? Where does it go

1985 gmc k2500 4wd vinM 350ci

Alright driver side of firewall in engine bay there is a 20amp glass fuse. Coming off it is a red 14gauge wire. It's about 3 feet long. It seems like it goes into the cab. It has a constant 12v. Idk where it goes. Can't really find it on the wiring diagram and I'm a little confused with some abbreviations in the wiring diagram. For some reason I think it's 4wd related idk.

Anyone got an idea?
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Old 07-14-2013, 05:40 PM   #2
bigd65
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Re: Red 12v wire?? Where does it go

Probably an add on for a stereo or something... GOT A PICTURE ????,
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Old 07-15-2013, 12:49 PM   #3
88Jimmy4x4
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Re: Red 12v wire?? Where does it go

ya thats probably for an amp, cb radio, snow plow, winch....could be anything but its def not factory
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Old 07-16-2013, 07:24 PM   #4
1985GMC
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Wink Re: Red 12v wire?? Where does it go

It's factory wiring. If u look at the wiring diagram "cab interior page 2" u can locate it.
http://www.73-87chevytrucks.com/tech..._V8_engine.jpg

I think it's above generator, then to the right of the generator on the same wire it says k/81 & k/85 only??
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Old 07-17-2013, 12:19 AM   #5
JellyBeanDriver
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Re: Red 12v wire?? Where does it go

Our 86' has that and it's the +12V feed for the trailer wiring.
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Old 07-18-2013, 10:40 PM   #6
motornut
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Re: Red 12v wire?? Where does it go

I've got one runs front to back red thick in the harness to the back hitch area
in my 79 jimmy,told it was for the trailer,prob gona put a lighter plug back there using it
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Old 07-19-2013, 07:57 AM   #7
chengny
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Re: Red 12v wire?? Where does it go

Camper or heavy duty trailer package:

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Old 07-20-2013, 08:45 AM   #8
1985GMC
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Re: Red 12v wire?? Where does it go

Thanks everyone very helpful. The trailer hitch idea makes a lot of sence. My truck is a vin M(heavy duty)
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