Troubleshooting Trailer Running Lights Not Functioning

Question:

I have a 2000 Chevy Silverado 2500 with a factory 7 way trailer plug. I have a small utility trailer with led lights. If I plug in my 7 way tester, everything works fine. Tails, turns, stops, reverse, electric brakes, and 12v charge. If I plug in my trailer lights, everything except tails work. The trailer lights work fine. I verified with a different truck. Now the interesting details: Last year, I changed my flasher relay to a tridon ep29 flasher relay for Leds. Everything on the truck works. Sometimes, when Im unplugging my trailer, the tail lights will flicker. When I seen that, I decided to do surgery and cut the plug off of my trailer and hook each wire individually. With the ground wire connected, if I hook up the tail circuit, it works. If I leave the ground and tail circuits connected, and hook up the left or right turn/stop circuit, I lose my tail. The big question is why? Is it possible the led rated flasher is causing the issue? Im losing my mind a bit.

asked by: John

Expert Reply:

It has to be a weak ground that's preventing the running lights from working. Typically when the running lights of a trailer are on the amperage draw is at it's peak since the vehicle running and headlights are on as well.

If you can improve the ground of the trailer you'll see the problem go away. If the lights ground through their assemblies make sure they are attached to a clean part of the trailer frame. Or you can run jumper wires from the assemblies to the main harness of the trailer.

expert reply by: Jameson C