Troubleshooting Only Center Running Light Working on Trailer

Question:

We have only the center running light lit up but the remaining ones will not light up. Can’t figure it out. Any ideas?

asked by: Tammy V

Expert Reply:

If you have one running light on your trailer lighting up then the trailer is definitely receiving power. What you need to do is test the ground connections for the rest of your lights and make sure they are securely connected to a clean, bare-metal surface as well as the wiring (especially where they are all connected to the main running light circuit). You can also test the lights themselves by applying 12V power to them to see if they still work individually.

Sometimes there are simply too many lights on a trailer and the tow vehicle isn't able to send back enough power for all of them but if your trailer lights were working just fine before then I suspect either bad grounds or burned out bulbs to be the issue.

expert reply by: Jon G