Trailer Lights On Older Trailer Not Working With New Wiring

Updated 06/13/2022 | Published 06/10/2022

Question:

I have an older Harbor freight trailer. The frame has some rust on it but nothing out of the ordinary. I just put all new lights and wiring on it. I cleaned all grounding areas and checked each light individually. But they will not work. I exchanged them and still the same process. My truck plug and fuses are fine. On the side marker lights they give off a faint light when I turn my lights on but you can barely see it. Ive also tried plugging them into my wifes new truck and still no luck. Any help would be greatly appreciated!

asked by: ROB V

Expert Reply:

If you've already verified your trucks trailer plug and it's fuses and have ensured that they are in good working order, then the issue is with the trailer.

Since you've already verified the grounds, I recommend also running a jumper wire from the trailer tail light to the vehicle to eliminate the chance of a potential bad ground connection.

If your jumper wire causes your lights to work, then you have a bad ground in your trailer's circuit. You can use the same jumper cable to test the grounds at different points on your trailer.

I have also attached a couple FAQs on trailer wiring that has some more troubleshooting and tips for you to check out as well.

expert reply by: Bryce D