Determining Wire Functions on Vehicle with 4 Wires and Trailer with 5 Wires

Question:

i have a standard yellow, white, green and brown on the truck trailer has white ,yellow ,green and black with yellow tracer and black with green tracer,how do i connect all this

asked by: Tim

Expert Reply:

Starting with the vehicle side wiring, it sounds like you have a standard 4-Way wiring connector installed. On a 4-Way flat trailer wiring harness, yellow is for left turn signal, white is for ground, green is for right turn signal, and brown is for running lights.

Then on the trailer side, it sounds like you may have a 4-Way wishbone harness, which splits the running light circuit at the connector. Most likely, the colors you mentioned have the following functions:

White = Ground
Yellow = Left turn signal/brake lights
Green = Right turn signal/brake lights
Black w/ yellow = Left side running lights
Black w/ green = Right side running lights

I do recommend testing the wires on your trailer to confirm this. You can use a spare 12V battery to test each of the wires for function, as going by color alone is not always the best method.

If the connector on your trailer actually has a 5th pin, then the 5th pin likely goes to an electric reverse lockout solenoid, which would typically be needed on a boat trailer. If this is the case, you will just need an adapter like # 20036 to go from the 4-Way on your vehicle to the 5-Way on the trailer.