Papa & Mimi
Mount Pleasant, SC,
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Joined: 03/25/2003
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I have a 2005 GMC Sierra 2500HD truck. I tow three trailers with this truck. Our camper, the boat trailer, and a utility trailer. Today I am working on the boat trailer. And find a strange condition with the lights.
I am using the GM provided 7 pin to 4 pin adapter. I plug the adaptor into the 7 pin receptacle at the bumper of the truck. Then I plug in the boat trailer plug into the adaptor.
Here is what happens:
With head light OFF,
Right turn signal works.
Left turn signal works.
Brake lights work.
With head light ON,
Both lights come on.
Right turn signal works.
Left trun signal works.
When I push the brakes both lights go out.
So now I hook up the utility trailer. It's lights do the same thing and the boat trailer lights.
So now I take the adaptor off and plug the camper's 7 pin plug into the 7 pin receptacle. The camper lights work just like they should. When I have the lights on and hit the brakes, the brake lights come on.
Any ideas what could be wrong?
Thanks in advance for any suggestions and/or help.
Papa
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Rollincool
Always Rollin
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Sounds like a bad ground on the boat trailer.
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goodcruisin
Greenwood, IN
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I'd return the adapter and get a new one. Probably an internal short was created when it was molded together.
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Jim&Peg
Central Ohio
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I agree that the ground is the most likely. Since it happens with both trailers using the 4 pin adapter, it is likely that the ground connection in the adapter is defective. To test, plug in one of the trailers and hook a piece of wire between the truck frame and the trailer frame. If you have jumper cables that is the easiest way to connect them.
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midnightsadie
ohio
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the ground is the most troublesom thing in wiring . the ground at the trailer or the light itself being the ground , I cut the wire ,drill a new hole and install new screw and a wire tab . some times you have to pull the lights off and clean up the mounting post ,also the hole where the light mounts too. boat trailers more than others.
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tvman44
Southwest Louisiana
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Bad ground.
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plascell
Lynchburg, VA
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I have a 7 pin to 4 pin adapter plug too. But it is special only for use with U-Haul trailers and their wiring. But I forgot the difference since it was 9 years ago when I used it last. Are we sure you have the correct adapter for the application? If it did work and failed, then I would agree to look for defective ground.
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NGRRFan
Colo. Spgs., CO
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plascell wrote:I have a 7 pin to 4 pin adapter plug too. But it is special only for use with U-Haul trailers and their wiring. That is a universal 7 to 4 adapter, not specific to U-Haul. It should have an extra wire on it with an alligator clip to provide a better ground than what is provided by the hitch.
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Papa & Mimi
Mount Pleasant, SC,
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Thanks to everyone for your reply to my trailer wiring problem. I re-mounted the boat trailer lights to insure a good ground with the trailer. Then I found the ground wire cut. So I re-attached that and now the work.................just like they are designed to do.
Thanks for everyone. It was a grounding problem.
Appreciate all the help.
Papa
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