How to Determine Which Wires are for Which Functions When Wiring Trailer to a 7-Way

Question:

My trailer lights have a blue,green,brown and white wire coming out of them.what color is for what when wiring them up to a 7 pin wiring harness?

asked by: David

Expert Reply:

Typically a blue wire goes to the brake controller, the green goes to the right turn signal, brown goes to tail/marker, and white is ground. The thing that you have to keep in mind when doing any sort of wiring is that not all colors mean the same thing. Sometimes whoever did the work just uses whatever wiring they have lying around.

The only wire that I would say is the safe bet is the white being ground since this is almost universally known. To confirm which wires are for which functions you will need to use a 12V power supply to see what functions happen when each wire is given power. You can verify the functions on your tow vehicle's 7-Way by using a Circuit Tester # PTW2992.

If you need a 7-Way connector on your trailer side you can use part # A7WCB or part # H20044 depending on if you need additional wiring or not.

I have attached a picture and a link to a helpful article on wiring that you can reference.

expert reply by: Jon G