How to Wire 4-Pole Connector on Trailer Has Extra Running Light Circuit

Question:

My 2008 Nissan Xterra plug has 4 wires going into it. The current trailer wire kit has 5 coming out of it but I just bought a new wire kit to redo the trailer. The new trailer kit only has 4 wires....how do I run this? My buddy said the ground would act as the second wire for my tail light current setup has two per taillight and the ground attached to the tongue and I needed to ground out the mounting bolt from the light. Is this right?? My mind is freaking blown....

asked by: Ryan D

Helpful Expert Reply:

It sounds like what you currently have on your trailer is what's known as a wishbone wiring harness. The running light circuit has two wires, one for the drivers side of the trailer, the other for the passenger side. A wishbone harness can make for a neater install, but they're not absolutely necessary. You can use a standard set up with only one running light circuit. Simply run down one side of the trailer, connect to the running lamp and splice in another length of wire to run over to the running lamp on the other side of the trailer.

I've provided a photo showing the difference between the two connectors, and I'll link you to our trailer wiring FAQ article which I'm sure you'll find helpful.

expert reply by: Mike L