Troubleshooting Wiring Issues on a Older Trailer

Question:

Hey there! Was told when I bought the trailer that lights worked, no issues. Of course that turned out not to be the case. Rear lights were old and could barely be seen when brakes are applied. Bought and installed LED that bit those slots 1157 and 194 168 compatible. Marker lights both blown out, will need new ones... Running lights working. Blinkers working. Hazard working. Brake lights work when running lights are off trailer only. My issue has to do with pressing the brakes while the running lights are on, when applying the brake when running lights are on, the lights turn off. When the brake is let up the lights turn on. I first assumed that maybe the 3rd lights in the back middle of the trailer was the designated brake light but after reading some other people plights and the fact that when the brakes are applied it shuts off the lights which tells me the brakes are indeed affecting the left and right brake lights. I found the ground at the trailer connection was broken. I spliced this and grounded it under the 17inch top nut that holds the wheel. Both rear lights are grounded to one of the nut/bolt of the brake light housing. Marker lights have been removed so they are not grounded at the moment. What did I miss? Thanks!

asked by: Logan S

LED Light
(click to enlarge)

Expert Reply:

Hello and thanks for the picture! My first thoughts when reading all of this was a bad ground so happy to hear you found that problem. Hopefully you cleaned off the metal before you attached the new ground. I still think your problem lies somewhere in the wiring with a fault or potentially another grounding issue.

Since it's an older trailer I recommend going over all the wiring searching for any faults or crimped wires. You could have a bare wire hitting some metal causing a surge when hit your brakes. Depending on the condition of the wires and what they're made of it would be a good idea just to replace it all. If you decide to do this you can use the 18-Gauge 2-Wire Bonded Parallel Conductor Wire item # SWC97FR for the lights and item # 12-2-1 for the brakes.

expert reply by: Jerred H