Boat Trailer Lights: Troubleshooting Problems

Boat Trailer Lights: Troubleshooting Problems

If you own a boat trailer long enough, you’ll have some issues with the lights… 

Just last weekend, while hooking up one of my boats, none of the lights decided they wanted to work: no brakes, no blinker, nothing was working. (This very trailer worked flawlessly two days earlier.) I scratched my head for a moment and immediately found the ground wire. Sure enough, it had become disconnected from the trailer itself. Problem solved.

Here are five relatively simple fixes to common trailer ailments that could save you time before you drag your boat trailer to a mechanic, or worse, cancel or delay a fishing trip.

None of the lights are working #1

Check the fuse box in your car or truck. This has saved me many times. Pro tip: carry three or four extra fuses in whatever size you need for that specific circuit at all times. I’ve had trips where a fuse popped multiple times.

None of the lights are working #2

Your 4-way plug connector has gone bad, or the contacts are incredibly dirty. I also carry a spare one of these in the glove box for troubleshooting. If none of the lights are working, clean the metal connections with a toothbrush and electrical contact-cleaner spray (or really anything you have around). Many of these actually have a small LED inside that lights up when connectivity is present. I like these, because if the LED is not on, it’s almost always a bad unit.

None of the lights are working #3

As mentioned above, a disconnected or damaged ground wire has been the problem with more trailers than I can remember. When all seems lost, double-check the ground connection on both the adapter and, more importantly, the trailer itself. In a pinch, I’ve taped it to the trailer or gotten creative with anything conductive to make the connection, until I can fix it properly. The ground can look different on all wiring harnesses and trailers, so try to familiarize yourself with which wire is the ground, and hopefully, avoid any headaches moving forward.

One light not working #4

Generally, this issue is caused by a bad bulb, if you’re using older incandescent-style bulbs. Familiarize yourself with blinkers and running lights and make sure to carry a few of each in your car. You can also try cleaning the connections with very fine-grit sandpaper and seeing if that works. Sometimes that’s all it takes. Beyond this, consider replacing the old incandescent bulb housing with newer LEDs. 

Lights working intermittently #5

This is the worst of all situations and not necessarily an easy fix, but it can be, if you’re lucky. Typically, this means there’s a damaged wire somewhere. Sometimes, the fix is easy to see and you can slice and patch a broken wire, but many times the wires are internally frayed, and you’ll never see the problem. My suggestion is to replace the entire system. Often, this is a blessing in disguise, as you can replace older incandescent lights with a newer, more robust LED system.