4 Pole Trailer Connector with Two Wires Connected to One Pin

Question:

I just bought a trailermotorcycle and it is a standard flat 4 plug except it has 5 wires one has 2 wires going to it. The male plug on the trailer side has the white wire which I gather is ground.It is cut off and hanging but all the lights work? Is the trailer grounded by the hitch or using the truck ground? What should I do?

asked by: craig t

Expert Reply:

As for the white ground wire that you mention, this wire should be firmly attached to a clean metal surface on the trailer. As the lights are currently working properly, you are most likely picking up the ground connection through the trailer ball. This is a pretty unreliable connection, and can lead to intermittent light malfunctions or failures.

Regarding the current connector on the trailer with the two wires running into one pin, some smaller trailers are wired this way. Instead of using one wire that splits off further toward the rear of the trailer to power the running light circuit, your connector simply joins both wires directly at the pin. If you were to replace the existing connector with the part # 18004 that you mentioned, you would simply run the brown wire to the running and side clearance lights as needed. You can either split the circuit into two legs, and run one leg down each side of the trailer, or run one wire down one side of the trailer, to the rear, and up the other side picking up each lamp as it goes.

I will provide a link below to our wiring FAQ page, which features some easy to follow wiring diagrams as well as other helpful information about wiring your trailer.

expert reply by: Mike L