Wiring issue - where do I start looking??

[scb1712]

Hi all,

I was trying to replace the plug on my trailer as I suspected that was the source of the intermittent lighting issue I was having. My vehicle is a standard 4 wire set-up and the trailer has a 4-wire plug with 5 wires coming in to it (see photo). Essentially there is a white (ground) connected to white on the vehicle, yellow to yellow, green to green, and the brown from the yellow pair and the brown from the green pair both connected to the brown on the vehicle. I wired up the new plug exactly as the only one was, only no tail lights or marker lights?? The turn signals and brake lights all work exactly as they should. Any suggestions on where I should start to look to solve the tail light issue??

 

[Watermann]

After testing your vehicle's plug get a wiring kit and rewire the trailer. A complete new harness is under 30 bucks and well worth the money.

 

[bruceb58]

Measure the voltage at the plug on the vehicle side and see what you have.

 

[seadogmike]

On the trailer side of the plug, make sure that the White is connected to the frame of the trailer with a good connection. Sounds like you may have a ground issue. Relying on the connection of the trailer ball isn't such a good thing. Just My Opinion.

 

[bruceb58]

Turn lights/brake lights work fine so not likely a ground.

 

[poconojoe]

I would make sure it's not your vehicle's plug first. It happened to me. My trailer's right turn signal wasn't working. I went crazy looking over the trailer wiring (thinking it couldn't be my truck). Turns out it was the truck. I disconnected the green wire from the truck's plug and ran a new one directly from the truck tail light. Soldered everything nice and I was good to go.

 

[MRS]

I have a trailer we use for hauling atv's it had the same setup till the dogs chewed up trailer wiring. I will check and see what I had to do but if I remember right I had to run the brown and brown/yellow wires together. Not yellow solid wire but the brown with yellow strip on it.