Determining Functions of Red, Black, Green, and Brown Wires on Trailer

Updated 02/27/2018 | Published 02/25/2018

Question:

Are trailer wire are red, black green and brown. The hookup wires are white, yellow, brown and green. What wire do we hook up?

asked by: Ray

Expert Reply:

It sounds like you are trying to match up the 4-Way wiring on your tow vehicle with the wiring on your trailer. Let me know if this is not the case.

The white, yellow, brown, and green wires that you mentioned coming from the vehicle represent standard trailer wiring. White should be for ground, yellow should be for left turn/brake light, brown should be for running lights, and green should be for right turn/brake light. Since the wire colors on the trailer side don't quite match up, I recommend simply testing them for function to ensure you make the right connections. You can apply 12V power (your vehicle's battery or a well-charged spare) to each of the wires on the trailer to see what function it activates, and then connect them to the corresponding wire on the vehicle.

Since trailer manufacturers (and previous owners) tend to switch up the color wiring they use, it is not always the best method to go by color alone.

expert reply by: Chris R