Why Do Some Trailer Tail Lights have 3 Wires and Some have 2 Wires

Updated 09/26/2016 | Published 09/24/2016

Question:

I bought a set of aftermarket LED trailer lights and it has wires coming out of the back that I never seen before. The colors are 1 red, 1 gray, and 1 white wires. Can someone help me out with this problem. I think I bought the wrong lights. Thanks

asked by: Tom M

Expert Reply:

A lot of trailer lights have 3 wires. One wire for running lights, one wire for turn signal and brake lights, and one wire for ground. Check the back of the light assemblies because it might indicate the functions of the wires.

Other lights may only have 2 wires. These lights will have a wire for running lights and the other for turn signal and brake lights. There is no ground wire because they ground through the mounting hardware.

If you can tell me the manufacturer and model number of the lights I can check to see if there is anything special about them or the wire functions.

expert reply by: Michael H