How to Wire Trailer Lights When Colors Do Not Match

Updated 11/10/2020 | Published 11/06/2020

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16 Gauge, 4 Conductor Bonded Parallel Wire - Per Foot

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Question:

My new 12 volt trailer light has red black yellow and brown wires. The wires on my trailer have are white yellow green and two Brown. How do I connect them?

asked by: Edward O

Helpful Expert Reply:

This is always a fun game to play. Unfortunately we can't always rely on wire color to know how to wire trailer lights. We can make a few educated assumptions, but I always recommend testing to verify.

Let's start with your trailer. My guess is:

White - Ground
Yellow - Left Turn/Brake Lights
Green - Right Turn/Brake Lights
2 Brown - Running Lights for both sides of the trailer

If the trailer wiring is already installed, then I strongly recommend hooking your trailer up to a truck and activate each light function while testing each wire with a circuit tester like part # PTW2993.

Your trailer lights are bit of a mystery. This would be much easier if I knew which lights you had, but you can also contact the light manufacturer and they should be able to tell you the wire function by color. Typically, brown is your running lights, yellow would indicate turn signal/brake lights, but it could also be a reverse light function if your light has that function. Red could be brake lights and black could be ground, but again, testing will be very important here. If you can tell me what brand and model light you have, or send me a picture, I'd be happy to look into more specifics for you.