What are the Functions of Trailer Light Green, Yellow, and Brown Wires

Question

Question:

Installing turn lights to a 4 flat trailer. Old original lights have 3 leads, Red, black and green. New Right side wires are Green and brown. New left side wires are yellow and brown. Which colors should be spliced together?

asked by: William I

0

Expert Reply:

Normally, the green wire on the right side carries right turn signal and brake light functions and the brown wire carries running light functions. On the left side, the yellow wire carries left turn and brake lights and the brown wire again carries the running lights. With only 2 wires, these lights must ground through the mounting studs.

Make sure to wire in the new lights by function to the existing trailer wiring and not by color.

expert reply by: Michael H

0

Line C.

5/24/2020

Hi! I only have 3 wires on the trailer (brown, white, green) and 4 on my Chevy van.. extra red.. How do I plug it in ? Thanks!

Reply

Chris R.

5/27/2020

The wires on your trailer aren't standard, so I really can't be sure how they would be hooked up to new lights or even up to a 4-Way connector. If the white wire is for ground, you're missing a wire. Is this a new (to you) trailer or are you simply re-wiring the setup? How did the signal lights work before if it's something you've had for a while?

Reply

Roger

6/1/2025

Appreciate your help! I’m wiring My boat trailer lights to the usual flat four plug I understand the color arrangements green yellow brown and white. However one wire is green on one side and brown on the other side. Where is it supposed to hook into? I have it with the green it’s that correct? Or brown? Or is it meant for a five flat? Thanks. Roger C ???

Reply

Robin H.

6/3/2025

@Roger a 5-way typically has a blue wire that would run to an electric lockout on a brake actuator. Wiring colors aren't always absolute but typically you have green for the right turn/stop and yellow for the left turn/stop with brown for the running lights. Do you have a brown wire instead of the yellow? How many wires are there total? If you have multiple brown wires it is still a 4-way but designed to run down both sides to make hooking up the running lights easier. If you are trying to tie in the existing wires on the trailer to a new 4-way connector I would simply trace the function to figure it out.

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Answer 2

You do have the wishbone trailer wiring setup. What that means is that if you have a solid brown wire it attaches to the brown and green wire as well as the brown and yellow wire. Yellow goes to left stop/turn, green goes to right stop/turn, and…

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Answer 4

You have it right so far, the 4-way connector is just as you have stated. Remember that Yellow has a L in it so that is the left side brake/turn signal and green has a R in it so that is the right side brake/turn signal. The colors for wiring a 7-way…

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Answer 5

Red, black, and white wires are common on many tail light assemblies. When this is the case, you will have red as stop and turn, black as running light, and white as ground. So you will connect yellow to red on one side of the trailer and green to…

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Answer 8

It is likely that the red wire on your old lights is the turn signal/brake light wire, and the black wire is the running light wire. That would make the white wire the ground. You can verify this by testing the wires using a circuit tester such as…

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What are the Functions of Trailer Light Green, Yellow, and Brown Wires

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