How Does Trailer Running Light Circuits with Yellow/Brown and Green/Brown Wires Run to New 4-Way
Updated 12/15/2025 | Published 02/21/2016
Question:
Trailer wiring has a green, yellow, a yellow/ brown, green/brown, configuration. The plug that I am using is a 4 prong, 4 wires, white, yellow, green, and brown. I have connected the yellow to yellow, green to green, which activate the turn signals, and the break lights. I have been unable to activate the tail lights. The brown green, brown yellow do not activate my the tails when connected to the brown wiring on the plug connection. Would a five wire, four prong plug be a better choice. The two Browns coming out of one pole.
asked by: John K
Expert Reply:
The yellow/brown and green/brown wires are the running light circuit on the trailer. The new 4-way that has a single brown wire can still be used but you will need to run both wires of the trailer to single brown wire on the 4-way. This is a very common way to wire up a trailer and it will work great for you.
If this configuration isn't working you will need to determine if the voltage is on the brown wire of your trailer when the running lights are on or not. If so, and still not working the issue is that the lights are grounding. If not, then the issue is corrosion, cut or exposed wire, or a blown fuse on the tow vehicle trailer wiring.
Joel P.
8/10/2020
Never mind-saw your later post. Guessing I need to splice the two browns into one wire as simply twisting them together has not worked. But I do have power at my tail lights.
Michael W.
12/13/2025
If I connect as you described above what do I do with the white wire
Jameson C.
12/15/2025
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Trevor
7/5/2020
So in our case, we have a 6x12 enclosed and all lights were working. The left fender got hit and tire away from the trailer, including the fender lights. The lights tore off the brown wire and the wire is now just sticking out of the trailer. None of the trailer lights are working now. Is this because there is no ground on that wire that tore away? In the short term, can we just ground that dangling wire until repair? All other wires appear to be fine. Thank you kindly.