Trouble With Trailer Lights Flashing Off and On When 4-Way Connected

Question:

I have been having issues getting trailer lights working correctly. I have a round 7 pin connector on vehicle that has an adapter to a 4 pin flat connector for trailer. Trailer has tail lights as well as running lights. I have tested at the vehicle and all seems fine. When I checked the trailer when I put on headlights and a turn signal all lights flash. So figure its a ground issue on trailer. I have cleaned and reattached ground. Same issue. Ran a wire to negative terminal on battery and the attached to trailer ground wire. All lights work great. Now what? Where do you think my issue could be or what my issue is? Appreciate the help.

asked by: Randy M

Helpful Expert Reply:

It sounds like the problem is in the wiring on the 4-flat connection of the trailer. I recommend the Hopkins Endurance Easy-Pull Harness # HM38134 to replace the 4-way plug on your trailer.

I'm guessing that there many be a connection issue at the 4-way or the ground wire inside the harness broke and this is what is causing your lights to flash. That is the last point and explains why your lights all work when you ran a dedicated ground wire to the battery. You can confirm that it is that connection by running the temporary ground wire to the ground on the 4-way connection to ensure that it is not the truck end connection or adapter that is damaged.

expert reply by: Bud M