Troubleshooting Trailer Wiring that Works with one Vehicle but Not Another

Question:

My home made trailer lights work OK with my factory 7 way connector through a 7 to 4 adapter. But for some reason my truck will not work with a friends utility trailer. He added reverse lights to his trailer with a 5 way flat, and has a 7 to 5 adapter. It works fine with his 2008 Tahoe. But when I connect, nothing works. If the GM factory 7 way connector is same on both, why will it not work with my truck?

asked by: Ricklz

Expert Reply:

Typically when this happens the issue is that the problematic tow vehicle has a weaker ground than the other one so when you go to tow a trailer that draws more you just don't have the ground strength to activate the trailer. Or it is possible the ground pin on either the trailer or the tow vehicle is bent or has some corrosion on it. Since all of the lights don't work the issue is going to be the ground though as that's the common circuit for all of them and when it goes bad it takes out everything.

You can also try improving the ground harness of the trailer and that might help as well.

expert reply by: Jameson C