Boats: How to Troubleshoot Simple Trailer Light Problems

Face it—if you own a trailer long enough, you’ll have some issues with the lights.  The longer you own the trailer, the more problems seem to pop up. Just yesterday 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 my ground wire. Sure enough, it had become disconnected somehow on the trailer itself. Problem solved. Here are five relatively simple fixes to trailer ailments that could save you time before you drag your boat trailer to a mechanic, or worse yet, cancel or delay a fishing trip!

#1 Issue: None of the lights are working

Check your 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 has popped multiple times.

#2  Issue: None of the lights are working

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 whatever you have around).  Many of these actually have a small LED inside that lights up when connectivity is present.  I like these because, if that’s not on, it’s almost always a bad unit.

#3 Issue: None of the lights are working

Like I 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, on 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. This is more often than not the issue with trailer light problems. The ground can look different on all wiring harnesses and trailers. Try to familiarize yourself with which wire is the ground and you can solve many headaches going forward.

#4 Issue: One light not working

Often times, this can just be 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.

#5 Issue: Lights working Intermittently

This is the worst of all situations and not necessarily an easy fix, but 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 wires are internally frayed and you’ll never see where the problem lies. My suggestion is to replace the ENTIRE system.  Sometimes this is a blessing in disguise as you can replace older incandescent lights with a newer, more robust LED system.

By Tim Romano.