Function of Brown Wire on 7-Way on Homemade Flatbed Trailer

Question:

Hooking up my trailer wires into the 7 pin connector. I am replacing my 7 pin cord and connection box, but unfortunately when I took my connection box out I forgot to take a picture of where the wires had been attached. It is a homemade flatbed trailer. The wires are yellow/brown, green/brown and another brown. I tied the y/b into the left signal/brake red at the connector box and the green/brown into the right signal/brake brown at the connector box. Nothing, no power. And what is the extra brown for???

asked by: Nora C

Expert Reply:

Even on manufactured trailers wiring colors can vary so there is no way to say for sure. The only way to know which wire is tied to which function is to trace the wire back. On an SAE standard 7-way the brown wire would be the tail/running lights. On an RV standard it would be the right turn/brake light. Since it is a homemade trailer it could be anything. I recommend tracing the other wires back, not just the brown wire, to see what they are connected to just to make sure you wire it correctly.

expert reply by: Robin H