Black and Red Wire Connection on Trailer Tail Lights

Updated 09/19/2026 | Published 07/14/2009

Question:

My tailights have two wires to connect to. They are Red and Black. So, for instance, I am running a brown and green wire to the rear right side. Do I connect green to red, or green to black?

asked by: Dan O

Expert Reply:

The black wire is for the running light circuit, and would be connected to the brown wire. The green wire would connect to the red wire on the lamp. On the drivers side, the black wire on the lamp would also connect to the brown wire for the running lights, and the red wire from the lamp would connect to the yellow wire on the trailer. We have a FAQ about trailer wiring that you might find helpful, I will include a link to the FAQ that can be found below.

expert reply by: Mike L

Mike L.

8/17/2025

Hello, I’m trying to connect trailer tail lights. The lights have red, green and black. I’ve tried all kinds of combinations but can’t get it going. Standard 4wire trailer wires.