How To Connect Vehicle 4-Flat Connector To Loose Trailer Wires

Updated 05/30/2018 | Published 05/27/2018

Products Featured in This Question

Hook Probe Circuit Tester

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Wesbar 4-Way Flat Trailer Wiring Harness - 20' Long

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Hopkins Trailer Wiring Installation Kit

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Wesbar 4-Pole Flat Connector w/ Jacketed Cable - Trailer End - 4' Long

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Question:

I have 4 flat connector and trailer has green brown yellow Brown white. How do i match these up? Truck has yellow green brown white

asked by: Danny

Expert Reply:

It sounds like your truck has a 4-way flat trailer connector with yellow, green, brown and white wires (see picture), which is pretty standard. It also sounds like your trailer has 5 loose wires that you are trying to connect to a trailer side 4-way flat connector similar to part # W787264.

If this is the case, then it sounds like your trailer came with a wishbone style wiring harness meaning you have two running light wires (brown wires) for each side of the trailer, the left turn signal and brake wire (yellow wire), the right turn signal and brake wire (green wire) and the ground wire (white wire). Normally, I try to avoid wiring trailer connectors by color because depending on the age of the trailer or how it has been previously used, there is a good chance that the wires have been tampered with. The best way to determine the function of each wire is to use a 12 volt power source such as a vehicle battery, ground it to the trailer and the ground wire and touch each wire to the positive post to see which tail light functions activate.

Once we know the functions of each wire, we can splice them to the 4-way flat trailer connector as follows. The ground wire will connect to the covered pin on the 4-way connector. The running light wire will go to the exposed pin next to the covered ground pin. The left turn and brake wire will connect to the next exposed pin and the right turn and brake wire will connect to the last exposed pin # 002220.

If I misunderstood your situation, please let me know what you have and what you are trying to accomplish and I'd be happy to offer further assistance.

I have a help article attached to help with 4-way connections.

expert reply by: Timothy G