

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 to Fix a Bad Ground When Boat Trailer Lights Are Not Working?
If your boat trailer lighting problems is not working, start by checking the ground connection. Run a dedicated ground wire from the plug harness directly to each light instead of relying on the frame for grounding.. 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
Common Reasons Boat Trailer Lights Stop Working & How to Fix Them?
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.
Avoid using Scotchlock or crimp connectors if your boat trailer lights are not working. Instead, use soldered connections with heat shrink tubing to prevent corrosion and improve longevity.
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.
Frequently Asked Questions
Why Are My Boat Trailer Lights Not Working?
If your boat trailer lights are not working, the most common causes include:
- Bad Ground Connection: A faulty or corroded ground is responsible for 90% of trailer light failures. Ensure a dedicated ground wire runs from the plug harness to the rear lights.
- Corroded or Loose Wiring: Saltwater exposure, moisture, and poor connections can cause wiring corrosion. Use heat shrink tubing and soldered connections instead of crimp connectors.
- Faulty Connectors: Flat-four and flat-five connectors are prone to corrosion and disconnection. Upgrading to a 7-pin or 8-pin round connector improves durability.
- Blown Fuse or Malfunctioning Tow Vehicle Wiring: If the trailer lights work on another vehicle but not yours, check the truck's fuse box and wiring harness for issues.
- Burnt-Out or Incompatible Bulbs: Ensure all bulbs are correct wattage and LED-compatible if you’ve upgraded to LED trailer lights.
- Power Issues from the Tow Vehicle: If the right-side blinker is dim or blinks fast, it’s likely a grounding issue or an electrical resistance mismatch in the vehicle’s flasher unit.
🛠 Quick Fix:
Before replacing parts, clean all ground connections, apply dielectric grease to connectors, and ensure the trailer frame isn’t being used as the only ground point.
Why Are My Boat Trailer Lights Not Working Even After Replacing Bulbs?
If replacing the bulbs didn’t fix the issue, the problem is likely a bad ground connection, corroded wiring, or a faulty connector. Ensure your wiring harness has a dedicated ground wire running to each light, and check for moisture damage inside the connectors.
How Do I Fix Boat Trailer Lights That Work Intermittently?
Intermittent trailer lights are usually caused by loose or corroded wiring, bad connectors, or grounding issues. Try cleaning all connections with dielectric grease, securing wires with heat shrink tubing, and ensuring the trailer is properly seated on the hitch ball.
Can LED Trailer Lights Solve Common Wiring Problems?
Yes, upgrading to LED trailer lights reduces common wiring issues because LEDs require less power, last longer, and are more resistant to vibration and water damage. However, they still need a proper ground and waterproofed connections for optimal performance.
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.
14 comments
Unplug your trailer lights before backing into the water, escpeially salt water. Not doind so will cause electrolysis and destroy your ground connections.
I broke the right light on my son’s trailer and the left one on mine, so I killed two birds with one stone when I got the set. These CZC trailer lights are of high quality and indistinguishable from the original submersible lights. I soldered the joints and covered them with heat-shrink tubing, which I recommend for a waterproof fix.
I had aground issue, turns out, the coupler on my trailer had rust build up, I cleaned it with a wire wheel attached to my cordless drill, the added die electric grease to help , the problem hasn’t returned, it’s been several years👍
I have 2013 Jeep Wrangler
Trailer issues trailer lights not working everything else works
Please comment
Fuse is fine
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