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12V + on trailer harness not working

ga1990

By ga1990
in Ask A GM Technician

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ga1990 Enthusiast

ga1990

Posted
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I have a 2003 silverado with the tow package. I just put electric brakes on my trailer, everything works fine except for the trailer disconnect wasn't charging...i tested everything and it turns out that the pin that is suppose to be 12V + on my truck is dead. I assume it is suppose to be hot as long as the truck is turned on? The battery from my trailer disconnect relies on this 12volts to charge...I've tried everything I could think of to make it to work(truck on, brake controller on, towing mode on) but still nothing. Is there a fuse somewhere for this or something else I'm missing? As you looking at the 7 pin plug, this would be the first pin to the right of notch at the top.

mcreyaufmiller Senior Enthusiast

mcreyaufmiller

Posted
Posted
I have a 2003 silverado with the tow package.  I just put electric brakes on my trailer, everything works fine except for the trailer disconnect wasn't charging...i tested everything and it turns out that the pin that is suppose to be 12V + on my truck is dead.  I assume it is suppose to be hot as long as the truck is turned on?  The battery from my trailer disconnect relies on this 12volts to charge...I've tried everything I could think of to make it to work(truck on, brake controller on, towing mode on) but still nothing.  Is there a fuse somewhere for this or something else I'm missing?  As you looking at the 7 pin plug, this would be the first pin to the right of notch at the top.

 

 

 

Check your owners manual for the fuse placment.

Trouttrooper Enthusiast

Trouttrooper

Posted
Posted

The fuse for that is in the fuse box under the hood. It's one of the big ones. They come from the factory without the fuse installed so I'd say it was either never put in or it blew. The positive pin at the back of the truck should have power all the time no matter what.

100R1 Enthusiast

100R1

Posted
Posted

On my friends '03 1500 we had to connect the 12 volt power / trailer positive wire in the fuse terminal under the hood.

 

You have to remove the plastic surround (shroud) in addition to the plastic lid on the fuse panel. then there is a wire that needs to be put on a post and bolted.

 

check your fuse cavity with a test lite, pull the fuse and check to see if you have power to the terminal before you remove the plastic shroud. if you do have power then you already have the wire connected. no power, then you need to connect the wire.

BADGERMAN Enthusiast

BADGERMAN

Posted
Posted

Check the fuse panel under the hood and find Stud #1 and check to see if has the red dummy fuse in it. If is does replace is with a 40amp (i think that is the size) fuse and it should work.

ga1990 Enthusiast

ga1990

Posted
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Posted

Thanks badgerman, that's what I did and now everything works....I don't know why they don't atleast tell you that in the manual...all my owner's manual basically said was "Stud #1: do not install fuse"

BADGERMAN Enthusiast

BADGERMAN

Posted
Posted

No Problem :P

There is also a topic going on about this, it should be close to the top of the new topic list and it kinds of explains it.

 

I just found this info out today on this forum.

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