Testing Trailer Wiring with Unknown Wire Colors to Determine Function

Question:

I have a hineese trailer light with 4 wires , without a white wire? What to do? Our colors are red, blue , yellow and black? How would we wire this one up?

asked by: Ken

Expert Reply:

You'll have to identify what the functions of each of the wire colors you mentioned are first with a tester like part # PTW2993 probing each of the wires while connected to a tow vehicle and applying the different lighting functions.

Standard trailer wiring light colors are white is ground, brown is taillight, green is right turn/stop, and yellow is left turn/stop. But if you are unsure what your trailer light color wire functions are you can try testing them by connecting them to a vehicle battery to see which wire illuminates which circuit. White to ground (most likely) and then the other colors to the positive post.

expert reply by: Jameson C