Troubleshooting Only One Trailer Light Working

Published 11/06/2019

Question:

Hello, I’m trying to wire a trailer from scratch. The old lights were put back on and all new wire. The only one that worked before is still the only one working. Do you think it’s just all bad lights except the one that works? Also what setting do I put on my multimeter to check if there’s actually voltage coming to the wires?

asked by: Gaines W

Expert Reply:

If you have replaced all of your trailer wiring but your lights still aren't working, save one, then I would have to think that you either need new bulbs or new light assemblies. Before swapping all of that out it would be worth testing your vehicle connector to make sure that it is sending power. I'm not sure what multimeter that you have but if you check out the attached photo of the 7-Function Digital Multimeter # PT89ZR I've highlighted where you'd connect the black and red wires as well as where the dial needs to be to make sure that you are getting power to your trailer connector. I have also attached some photos showing the standard pin location functions that you can reference.

Once you've verified that your vehicle is sending the power you can then move on to testing your new trailer wiring bu touching the red wire to your trailer wiring and your black wire to a ground source. If you get a reading then that indicates your bulbs/lights need to be swapped out but if you don't get a reading then something is going on with your wiring from your trailer connector to the trailer lights and you need to look for and fix any places where the wiring is bent or damaged.

I have also attached a link to our helpful article on troubleshooting trailer wiring that you can check out.

expert reply by: Jon G