Led trailer running light works, but not the brake light

[The motor guy]

Okay be flush mount led trailer lights that are held in place by a rubber grommet. Anyways, I find it odd that the running light portion of the light works, but the brake light portion doesn't. This is just this one light. All other lights on the trailer work.

I don't think it's a ground issue I think it's just the brake light portion of the light burned out.

Opinions?

 

[rubberchicken]

I would suspect the wiring, usually the connector at the tow vehicle or at the trailer. Do you have one of those trailer light test dongles ?

https://www.etrailer.com/Accessories-and-Parts/Curt/I26.html

 

[The motor guy]

Let me correct myself. Only the passenger side brake light doesn't work on the trailer. I have a 7 pin connector for this trailer.

 

[tahoe_hybrid]

check the wires

 

[supton]

Wiring.

Just went through this on a trailer, changed the bulb, no change. Finally found it. I must have dragged the wiring at some point, as 2-3 inches of one wire was rubbed away. It happens.

Sometimes you might just have to cut a wire, strip, then hit with a multimeter to see if you have voltage--if you do, the problem is closer to the taillights. If not, then it's closer to the tow vehicle. Get some of those butt splices, chances are, you will need them.

 

[mk378]

First Make sure the truck is OK e.g. check it with another trailer.

The brake / turn function of the two big lights on the back is separately wired to the truck so that turn signals can be implemented. For turn signalling the truck energizes one wire in a blinking fashion. When you step on the brakes, the truck energizes both wires at the same time so both lights come on steady.

The standard color code is a green wire for the right brake/turn and yellow for the left.

So a break in the green wire or a faulty lamp assembly will cause this. If the lights are easy to pull out, check the right one by substituting with the other one.

 

[The motor guy]

I fixed it. It was a bad light. I just unplugged the bad one and plugged in the new one, no wire cutting/splicing required. I love it! It's a three prong plug that's a standard across all brands because the new light wasn't even the same brand and it still plugged right up.

Those flush mount lights are awesome, they're held on by a stiff rubber boot/grommet and you just put the boot into the cut out, then shove the light into the boot and you're done, no screws or anything.

 

[The motor guy]

At the time of posting this I didn't realize all I had to do was unplug the light, otherwise I could have just switched them. Lol sorry.

 

[The motor guy]

I pulled on the plug the wrong way the other day, that's why I didn't think it was a plug.

 

[mk378]

These same lights have been used on big rigs for many years. The first ones were incandescent, after the bulb burnt out unplug the whole module and replace it. In cars, corrosion and bad contact between the bulb and the socket is a common problem. That problem was eliminated by soldering the bulb in place and sealing it in the plastic.

The LED ones have the same plug for simple upgrading. The plug and the size of the light (being two major types, round or oval) is industry standard.

 

[The motor guy]

This probably wouldn't work good if it was a boat trailer though. Those need heat shrink tubing. Or if some genius so just make it so you could have 25ft of wire coming out of the light with no breaks in between.

 

[mk378]

The trick to boat trailers is to de-energize the lights (unplug from the truck) before going into the water. You can also put a bunch of grease on the plug.

 

[The motor guy]

I don't both with led lights. Haven't had a problem. I've never had an issue with led lights on a boat trailer since I switched about 7 years ago. Heat shrink butt connectors are my secret. Plus the led lights are designed better.

 

[red7404]

check the grounds from truck frame to trailer frame. i have had to add a bigger ground wire to handle the current.