Troubleshooting Lights On Trailer That Was Rewired With Extension Cords

Updated 12/29/2016 | Published 12/28/2016

Products Featured in This Question

25 Ft 5-Way Trailer Wiring Harness - Wishbone Style - 30" Ground - 5' Auxiliary Wire

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Hook Probe Circuit Tester

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Question:

I recently rewired my dads 16foot trailer using extension cords. I used black for brown and white for blinkers. I grounded to frame at each light and again at plug in front of trailer. I should mention there are 4 lights on each side of the trailer plus one in the center on the very back. I ran a separate wire for the brakes, they work just fine. I added a 5-way plug and have a 7-pin to 5-pin adapter on the truck. All the lights come on except those that need new bulbs but right side blinker doesnt work and neither does brake. running lights work just no brake lights/blinkers. I put some weight on the tongue when I was crossing sides and i noticed the lights dimmed. Then when I took it out for a test drive they got really dim during turns and accelerating. Im thinking it could be a grounding issue because there was rust on some of the grounding spots and im using ring terminals with self-tapping screws to go into the frame. What could be another issue? Im completely stumped on this one. Please help!

asked by: Josh P

Helpful Expert Reply:

It does sound like you have a ground issue and when making turns or adding weight the ground is losing connection or wiring is shorting out and causing the problems you see. I do not recommend using extension cords that have 2-wires to try and wire all of the lights on a trailer. You will need a circuit tester like part # PTW2993 to test the wiring as someone runs through the functions when the trailer is connected to the tow vehicle. Loose connections, wires shorting out on the trailer, or mis-wired connections can cause all sorts of problems.

I do recommend using a wire harness that is designed to do the job correctly and has wires that are colored so it makes it much easier to make sure you run the wires as they should be done. I recommend a wiring harness like part # A25W5B. This harness has a 5-way connector and is 25-ft long. It also has a 30-ft long ground wire.

I have attached a helpful article that shows how wiring should be run on a trailer you can check out.

expert reply by: Jeffrey L