Troubleshooting Trailer Lights that Stop Working When Headlights Come On

Question:

I have just completely rewired our gooseneck trailer and I have brake lights, turn signals, and running lights along the side of the trailer. The tail lights are the only lights I do not have. If I have my hazards or a turn signal on and turn on my headlights then I will loose the turn signals or hazards on the trailer. I am thinking it is a grounding issue so I took a grinder to clean a spot and grounded a set of tail lights directly to the trailer itself instead of through the wiring harness to the truck. Same results. I also Teed into the ground by the plug and ground the the trailer neck as well. I have also checked the hot/tail light feed all the way back to the taillights and it is hot. I am at a loss and am not sure what could be going on. Any help would be greatly appreciated

asked by: Wade D

Expert Reply:

It's typically a ground when the problem you described appears. The other possibility is that you are over drawing the circuit and when the headlights are on it pushes it over the edge. Is the ground pin of the 7-way connector clean and free of corrosion? Is the pin possibly slightly bent? Also check to make sure the ground pin of the tow vehicle's wiring is good too.

expert reply by: Jameson C