How To Identify Functions Of Trailer Wiring With White, Yellow, Green and Red Wires

Published 11/03/2023

Products Featured in This Question

Hopkins Endurance Easy-Pull 4-Way Flat Connector w/ 48" Harness and LED Tester

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$10.07

Hopkins Endurance Easy-Pull Harness with 4-Pole Flat Connector - LED Tester - Trailer End - 12"

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$9.60

Question:

I have the wires coming from my truck is green brown white yellow on my trailer it is green white round yellow and red what did the Red Hook to

asked by: Randy

Expert Reply:

The most logical explanation is the shop that built the trailer used a red wire in place of the brown but as not all shops have to abide by a particular set of wire colors on trailers it is best to ensure what the wires run to. You can determine the wiring functions by either tracing the wiring or using a battery to jump the wiring and verify its functions. Typically on 4-way wiring the white is the ground which will run to every light or it will connect to a ground on the trailer. The yellow is generally for the left turn signal/brake light and the green is generally for the right turn signal/brake light. Your red wire may be for the running lights which is generally what the brown wire functions as.

We do have the Vehicle End # HM48058 and Trailer End # HM48138 connectors which both have LED test lights and EZ pull rings on the connectors to make troubleshooting and disconnecting much easier.

expert reply by: Bud M