Why Does my 4-Way Connector Have 2 Wires Ran to One Prong for the Tail Light Circuit


my trailer has a 4 wire flat connector but there are 5 wires entering it including the white ground wire. This end plugs into a 4 wire flat connector of my 2004 Tacoma. I need to replace the trailer connector end because the wires are broken but I cant find a 4 flat connector that has 5 wires going into it. It looks like 2 of the wires go to one of the prongs and the other wires go to dedicated prongs. How can I wire this using a standard 4 flat connector on the trailer wire harness or will I have to locate a 4 flat connector that actually has five wires going in to it?

Expert Reply:

It sounds like you need an Optronics wishbone wiring harness, part # A35W42B. This 4-Way has a prong that has two wires that come out of it.

The reason some 4-Ways have two wires coming out of one port is because that prong represents the tail light functions for both sides of the trailer. So one wire would run to the tail lights on one side of the trailer, and the other wire would run to the other.

I attached a video below that shows this product being installed onto a trailer and explains how the two wires from that connector work.

You could also use a standard 4-Way that has only one wire on it per prong, but you would need to splice the two wires that previously ran to one prong into one wire, and then run that wire to the tail light function port of the 4-way. If you went this route, I would recommend you get a 4-Way trailer end connector, part # 18004.

I attached an FAQ article on trailer wiring below that you should find helpful.

expert reply by:
Jameson C

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