Boat Trailer Lights Problems—Advice from the PartsVu Community

Recently, we shared our “Troubleshooting Trailer Lights – A Boater’s Dilemma” article with the PartsVu community on Facebook. A lot of you commented with some really helpful feedback, and we wanted everyone to benefit from these boat trailer lights problem-solving insights.

How do you fix a bad boat trailer ground?

As we know, and many of you agree, trailer lighting problems are often a problem with the ground. Richard MacClugage from Marathon, FL, commented, "90% of the problems are bad grounds.”

But what can we do to fix trailer grounding problems? The following are some great suggestions.

"Trailer lighting problems are almost always a connection or a grounding issue. Run a ground wire from your plug harness to your rear lights (don't depend on a frame ground), and crimp/heat shrink all the connections. I've learned this the hard way."

Mike F., Savannah, Georgia

"Place a piece of steel wool on the ball, then attach the trailer." (to help with ground problems)

John S., Tomah, WI

“Get LED trailer lights, seal all connections, and work from a secure ground. That will address 99% of all trailer light issues.”

George S., Jackson, Mississippi

“Make sure the trailer is seated on the ball. Move it back and forth before you check your lights.”

Mark Q.

"And after you have done what the troubleshooting trailer lights article suggests, run a dedicated ground to every light fixture. In my opinion, using the chassis for the ground is lazy and unreliable, but that's the way all of the trailer manufacturers do it."

Richard N., Gainesville, Florida

“Most trailer light issues are related to bad grounds either on the trailer or tow vehicle. I've been wiring trailers for 30 years and I always ground to each light with ground wires. All exposed wire goes in a spiral loom. Harness ground ties into ground wires for lights, and ring terminal ties everything to the tongue, stainless machine screw, solder, and shrink wrap all connections. Happy customers and no warranty work."

Kristian S., Utica, NY

What are some other ways to avoid boat trailer problems?

While grounding problems cause the bulk of the trailer lights issues, other problems do arise. The following are some great insights that will help you look out for common issues.

“Get rid of all the Scotchlock connectors, crimp connectors, and solder wires and use heat shrink tubing. Too many people take short cuts.”

Lee H., Yankton, SD

“Rule #1 - solder all splices. No 3M Scotchlocks!”

Paul L.

“My # 1 rule is to take those flat-four or flat five-wire harnesses, cut them off and throw them in the trash. Then get a quality round 7 or 8 pin connector for both the tow vehicle and the trailer. I have never had problems with 7 or 8 pin connectors but was constantly struggling to keep the cheap flat-four, and flat five-wire harnesses clean, corrosion-free, and working.”

Colin Watkins, Casstown, OH

“Use dielectric grease to avoid problems. Do not under any circumstances use WD-40 to clean a flat 4-pin connector because it will corrode them quickly.”

Tom D.

"The issue is putting the trailer lights in the water while they are on. This causes electrolysis to the ground. So, unplug your lights, and they will last longer. Also, move all connections above the waterline."

Carl N.

“If you are having problems, do not try to fix the old wiring—most manufacturers put in crimp connectors. Rip them out, put them in new with only soldered and shrink-wrapped connections, and replace all your lights with LED sealed lights. This will allow you to avoid problems for years.

I rewire boats and trailers. I recently rewired a Triton boat trailer, and it had 21 push-on crimp connectors inside the trailer frame. This is where the problems originate. I only use crimp connectors for a quick on the road fix, then fix it right when I get home.”

Dennis P., Milford, IL

An Interesting Trailer Lights Problem—the Community Stepped In to Help

“Here's a problem for you, knowledgeable people out there. First, let me say that I have installed trailer wiring and hitches professionally for about five years and have a background in car audio and everything 12vdc.

Here is my issue, I have a 1997 Ford 150, my factory towing system is dead except for the 12v battery feed and electric brake circuit. I ran directly from my taillights to my 7-way plug and separate flat-four and if I have my lights on, the right-side blinker is very dim and fast blinking, the left is fine.

I have a new ground wire anchored directly to the truck frame connected to the 7-way plug and the dedicated flat-four. The trailer lights work perfectly on other vehicles. I've upgraded to LED bulbs on the trailer; the right side still blinks fast if the truck’s lights are on.

What am I missing? I've also tried a jumper directly to the battery ground terminal as well during my quest for proper function. I have soldered connections and have all new plugs and housings on the tow vehicle.”

Tom D.

The PartsVu Community Weighed In

“It’s still a bad ground.”

John S.

“I agree that it is a bad ground. In addition, make sure all bulbs are of correct candle power and have an appropriate flasher. Yes, a lot of stupid things will affect the operations of lights.”

Vincent G., Sr.

We found these comments and advice from the PartsVu community to be quite valuable, and we hope that they are interesting and useful to you all well. Additionally, PartsVu has a collection of trailer articles on a range of topics that we invite you to explore. Explore trailering articles.