Boat Trailer Light Troubleshooting

[TroutFisher87]

I'm sure everyone can relate to faulty boat trailer lights, and I'm having some difficulty troubleshooting mine. I ran my green wire to my right turn signal light, the yellow to the left turn signal, and a brown to the left tail light. I used a jumper wire to get to the right tail light. I connected the white ground wire back to the tongue of the trailer about 2' from the wiring harness.

The issue I'm having sounds like a ground issue, but I'm not sure. Only one of the tail lights is working, the left turn signal works when I turn on the left blinker; however, it continues flashing when I use my right blinker as well. The right turn signal does not work at all. The left brake light works well, but the right brake light does not work or is really dim.

I've tried the boat lights on 3 different trucks to make sure it wasn't just my truck and I'm getting the same results. Also, I've tested the trailer lights by hooking directly to a battery (the ground to the negative post and the yellow, brown, and green to the positive), and the lights worked perfect when I tested each of them individually. I thought it might be that the grounding through the trailer was not correct, so I've ran ground wires from the post on each light back to the white wire ground on the trailer. In this way, the lights are grounded directly from the tail lights back to the white wire coming out of the wiring harness. I'm still getting the same results, however.

Does anyone have any clue as to what the issue may be?

Thanks.

 

[limitout]

Re: Boat Trailer Light Troubleshooting

sounds like the jumper is causing issues for one light to be blinking when using both blinkers, the one light not working sounds like its a bad ground

I have rewired many trailers over the yrears and come to find the best way is to stop using trailer wires.

go buy a 50ft extension cord at the hardware store an cut the ends off and cut it in half, now use the green wire to the light mounting bolt for a solid sure ground and then the color code is white for light and black for blinker. you only need the plug connector on the front to make your connections. the whites get connected together to your plugs brown wire and the greens get connected together to your white ground wire from the plug. then you hook your yellow and green to the correct sides and your done.

this gives you a much heavier wire and it completely eliminates the trailer from needing to be your ground, it will also outlast any trailer wire you ever buy. you will never have another trailer wiring issue if you do this.

 

[TroutFisher87]

Re: Boat Trailer Light Troubleshooting

limitout,

I'm not sure how doing that is going to be different than what I've already tried. I've already taken two ground wires and wrapped them around the mounting posts of the lights and wired them into the white wire coming out of the wiring harness back at the tongue of the truck, but that didn't fix the problem. That sounds like the same thing when you're referring to hooking the green wires into the white wire from the plug, only different colors. Wouldn't that be the same thing? Am I missing something?

 

[Grandad]

Re: Boat Trailer Light Troubleshooting

Only one of the tail lights is working, the left turn signal works when I turn on the left blinker; however, it continues flashing when I use my right blinker as well. The right turn signal does not work at all. The left brake light works well, but the right brake light does not work or is really dim.

I'd recommend starting with fixing the most obvious and simple circuit. Since one tail light works and the other doesn't, I'd start by finding out why that one light isn't working. It could very well be a ground issue, but with multiple indications and the fact that you've already verified the grounding to some extent, start with a voltmeter or a spare 12 volt socket and bulb and check the tail light circuit. Electricity is logical, so you must approach the problem with one logical step at a time. - Grandad

 

[smokeonthewater]

Re: Boat Trailer Light Troubleshooting

99.999% of the time it is a ground issue.... your lights aren't grounded well enough... don't ever make a ground by wrapping anything around anything... use a (preferably heat shrink waterproof) ring terminal and a self tapping screw OR bolt and nut into the frame rail... OR you can use a ground wire all the way to the light plug.

 

[Grub54891]

Re: Boat Trailer Light Troubleshooting

Most lights ground through the mounting bolts,BUT, some only use one mounting stud for the ground. Mabe ya used the wrong stud? And yes to proper connections,shrink tube or shrink connecters.

 

[kenmyfam]

Re: Boat Trailer Light Troubleshooting

Posted this many times.
3 biggest issues with trailer lighting are as follows
1. Bad Ground.
2. Bad Ground.
3. Bad ground.

Assuming you are wired correctly to begin with.
Start tightening up all trailer frame bolts and see what happens.
Good Luck

 

[limitout]

Re: Boat Trailer Light Troubleshooting

limitout,

I'm not sure how doing that is going to be different than what I've already tried. I've already taken two ground wires and wrapped them around the mounting posts of the lights and wired them into the white wire coming out of the wiring harness back at the tongue of the truck, but that didn't fix the problem. That sounds like the same thing when you're referring to hooking the green wires into the white wire from the plug, only different colors. Wouldn't that be the same thing? Am I missing something?

if you ran the wire from the light all the way to the plug that "should" have solved it for you if it was a bad ground so you need to try using a wire to connect both posts of the light as mentioned in case you use the lug that isn't connected to the lights ground.

you may have a bad bulb in that light so even if it looks ok switch the bulbs, if the problem is still there switch the whole lights and if you still have the problem you have confirmed its the wires that are bad.

the way I described was to simplify it by just starting over with everything new.

 

[Jake007]

Re: Boat Trailer Light Troubleshooting

Sounds like you verified the lights work when direct wired, new wires did not solve the issue.
One thing that has bit me in the past was the actual connector, looked good but was intermittent on the circuit. Try spraying electric cleaner on both the truck connector and the trailer connectors and see if that fixes it. Likely you will need to replace the truck connector or the trailer connector with a new one. I run in salt allot and have this problem with the truck plug in connector every year or two. I will use the spray once or twice to keep me going and then I will just replace and I am good to go again.

 

[I`mNotMe]

Re: Boat Trailer Light Troubleshooting

Yes. Could be ground (or bad connection of ground).

It is rare but sometimes, a light assembly can internal short and create back-feed into a different wire. Thus, causing weird behavior.

As a suggestion, remove wires from both rear light assemblies. Connect marr connectors on each 12V wire - so it doesn't dangle and accidently short out. Now, visual test fender lights. Visually test tongue lights. Visually test ID Light bar - under rear of trailer. If all is good with those little lights, use 12V probe tester and test the each light assembly disconnected wires. Test 1 x wire at a time. If one side tested clean, then test the opposite side wires. Are all wires properly delivering 12V current? If yes, connect 1 x light assembly. Check all lights. Is that connected light assembly ok? If yes, do same with other light assembly. Is that connected light assembly ok? If wondering, this is called "individual unit testing". re: Test the wire runs. Test the little marker lights, test 1 x light assembly, then test other light assembly.

Hope this helps.