Submersible LED taillight issues

I have a Genesis galvanized trailer that's in really good shape. It's built for a 12ft boat, but I extended the bunks and moved the jack stand and winch forward on the tongue to accommodate my 14ft boat.

I removed the junk taillights and wired in new Blazer (I think that was the brand, from TSC) LED lights. Also replaced the yellow marker lights on the tongue.

Here's the problem: I have no taillights when the headlights are on. Turn signals and hazards work. I thought my trucks trailer wires were bad, but it does the same thing on my dads truck too. We checked the ground, it's good. Even took it off and reattached it to make sure.

We could be missing something, but we think we've checked everything there is to check. What should we do? A buddy of mine also had some issues with LED lights, but I don't remember how they fixed it.

Any help is greatly appreciated.

Re: Submersible LED taillight issues

What kind of truck?
I was having a problem like you but it was my stop/turn signals. I have Chrevy with a towing package. It turns out on GM towing packages the trailer connection has it's own fuses. Check your fuses, if the trailer fuse is burned out, all of the car or truck lights will work but the trailers will not.

Re: Submersible LED taillight issues

You really need to break out a voltmeter and see where the power goes away. A 4 prong trailer tester also can help out and verify your wiring. It doesn't sound like a ground issue but likely mis-wiring on the trailer... just a SWAG on my part.

I use this website as my guide for wiring problems: http://www.etrailer.com/faq-wiring.aspx and good luck!!!

Re: Submersible LED taillight issues

I drive a 2000 Ford F-150 2wd, 4.2 L V-6. Dad and I were going to completely re-wire the trailer, but it's solid square tubing the whole way, so we tried to use the existing wire. The wire that's there is fire, there's nothing wrong with it at all. We noted the way every taillight and marker light was wired up, and hooked up the new lights the same exact way. LED's use less voltage than incandescent lights, right? There shouldn't be any lack of power problems, correct? Like I said, the taillights don't work on my truck or my dad's truck. He drives a 1999 Ford F-1504 wd, 4.6 L V-8. He's never had any issues with our other trailers, so I'm ruling out the truck wiring.

Re: Submersible LED taillight issues

Ok, assuming a four-flat plug here....

There are only three circuits: left turn, right turn, and tail. Markers tap into the tail circuit. All go to ground on the trailer frame, which goes back to the tow vehicle.

Sounds like the ground is ok, which only leaves one possibility....broken wire(s).

Are the markers working correctly? Then the break is past them, in the frame.

Best bet is to run new wire all the way through. Use the old wire to pull the new through the frame, or a fishtape.




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Re: Submersible LED taillight issues

I am not sure if this helps but some LED lights only work one way. What I mean is the polarity must be right. If I thought my wiring was good I would disconnect one apply 12v to the ground wire and ground the hot wire for the light. If it comes on then the led's must be assembled wrong.

Re: Submersible LED taillight issues

I had a similar issue when rewiring my trailer. I took and grounded EACH light to the trailer and then ran a ground line from the trailer to the plug. That way I had a good ground from the plug to the trailer. I had been having the fuse for the trailer plug blow on my Ford Ranger due to an intermittent ground. The blown fuse would kill my all the lights, but the taillights would go first due to bad ground.
Don't count on a single ground point (plug to trailer chassis) to give you a good ground for everything on the trailer. Better to give each its own ground.

Re: Submersible LED taillight issues

View attachment 101196Here is a "how to" on the wiring.

Re: Submersible LED taillight issues

Yes we're talking 4-flat, forgot to mention that. The marker lights aren't working either. The old ones were connected with those cheap wire connectors that have the sliding piece of metal you crimp thru the insulation. My guess is they may have broken the wire. We'll start by grounding everything first, check polarity, then move on to a re-wire if that fails.