Troubleshooting Trailer Wiring That Does Not Work with One Vehicle But Does with Other

Question:

I bought this in Dec but havent had chance to put in until now. Install went smooth. Lights on tow vehicle work as they should. I put a tester on the 4 prong end of the output and it is hooked up properly according to the tester but when I attach it to the trailer the lights on the trailer dont work.... I know the trailer lights themselves work because I tow it with my other vehicle 2x a week... Any thoughts?

asked by: Alexander C

Expert Reply:

Typically if trailer wiring works with one vehicle but not another and you know the wiring is working the issue is that there's just weak enough of a ground to cause the lighting to not work on the weaker vehicle wiring. So what you'd need to do is improve the trailer wiring ground on the trailer and you'll see the wiring start working again.

I attached a help article on trailer wiring for you to check out too.

expert reply by: Jameson C