Rewiring Trailer With 5 Pole for 7-Way Trailer Connector

Question:

how do you convert a 5 way plug along with an extra set of black wires that run into an electric brake system? The 5 wire has white, brown and yellow colored wires along with two black wires that run direct into the plug. But on the trailer itself, there are two black wires, seperate from the plug, one with red wrapping that are connected to the electric brake system on the trailer. How do I connect all these wires to a 7 way blade plug?

asked by: Blamberton

Expert Reply:

Electric brakes on a trailer would typically use 1 wire to feed the trailer brake assemblies.I'll link you to a help article that includes some wiring diagrams that you'll find helpful.

I'd recommend removing the 5 pole and installing a 7-way plug. The easiest and neatest way to do this would be to use a 7-way pigtail/junction box like # HS381-9000. Your white wire is likely the ground. As for the rest of the wires, you'd be best off applying 12-V from a car battery to each lead to see what that circuit powers. Typically your yellow wire will be for left turn and brake lamp and brown would be for the running lamps but I'd recommend testing to confirm since it sounds like your trailer might have non typical wiring. I'll link you to our trailer wiring help article as well as a product description video for the pigtail/junction box I recommended.

expert reply by: Mike L