Troubleshooting Trailer Wiring Not Working on Fiberglass Sailboat Trailer

Question:

I have a sailboat which has a fiberglass light bar which the lights mount to, an old bulb burned out, which was corroded in so I replaced the lights. I ran new wiring back to the light bar, with a new light kit. The new lights as expected have two wires coming out, brown/yellow, brown/green. No ground. Of course these lights are all made so they ground directly to a metal trailer, but I have a fiberglass bar with metal mounting posts. So the boat builder ran a ground wire between the left and right posts, and then spliced those two together and ran a ground forward into the white ground coming off the car side. Thats what I recreated, and Ive got no lights on the bar. Oddly enough, my car throws no errors, the car onboard diagnostics normally tells me on the dash if a given trailer light bulb is not working or burned out. Everything seems to say ground issue. I cut the wire running forward and attached the lights from the ground to the trailer, nothing. Attached the white right off of the car to the trailer, nothing. Both bare ends to the trailer, nothing. Tried taking the grounds off of the posts, nothing. The car side is good, I have full working lights on my utility trailer. Ive gone as far as being frustrated and buying an LED light kit, same problem. Im at a complete loss and traveling for a regatta in less than two days. Any help is greatly appreciated!

asked by: Matt

Expert Reply:

It does sound like a ground issue based on the trailer being fiberglass and everything else you have mentioned, but have you verified that power is making it back to the circuit? Use a circuit tester like part # PTW2993 to verify that the correct circuit is active. It's possible you have focused on the ground so much that the power circuit was overlooked. You also might try just running the lights directly to a battery to verify that they do work.

I also attached a help article on trailer wiring troubleshooting for you to check out as well.

expert reply by: Jameson C