Hey guys, the turn, emergency, and break lights of my boat trailer work fine but the running (night) lights won't light up. I found that my truck's fuse was blown so I replaced it. I tested the truck's plug with a multimeter and it has power now. However, the trailer's running lights still don't work. Any ideas on how to troubleshoot it? Where can I take the trailer to have it fixed? I'd like to avoid the boat shop because they charge too much.

Sounds like a wire shorted to the frame, trace the running light wire from the front to the back of the trailer looking for bare or broken wire and repair.

Did the truck blow the fuse again when you tested?

Bulbs ?? I have got into the habit of disconnecting the trl. lights wiring from the truck's wiring connection before I dunk the trl. . Fuses have been known to blow when the lights/bulbs hit the water. I also take off the lights lens and spray some lubricant on all metal parts inside. Adding a little grease to the seal helps with leaks also. good luck and tell us what you found out what the cause was.

I took the boat to the lake twice so the trailer was underwater after I replaced the fuse. It is still good. I even tested the connections on the other end of my removable tongue and got power there too so it looks like the problem is in the wiring of the trailer. I'll have to trace it like bronco suggested.

Regarding the bulbs, my trailer has 2 tail lights which are made of LEDs. I'm thinking that the tail lights are fine because they work when the turn or emergency signals are turned on. The trailer also have two orange lights: one on each side. Those only light up with running lights and they are not working.

most trailer light problems start with a bad ground

Do your brake lights work? That clears a bad ground. Your tail lights power the side lights and the clearance lights. Do they work?

Brake lights work fine. The 2 amber side lights and the 3-rear markers don't work.

Your ground is good, your brake light wire is good. The tail light wire is at fault.