Identifying an Unknown Wire on a Trailer when It Runs through the Trailer Frame or Body

Question:

Someone who previously towed our camper tore the trailer wires loose in several spots. I am going to redo the wiring but cant find where the blue wire goes on the 5th wheel. The only wires I have going to my brakes are the red and black from what I can tell

asked by: Joe

Expert Reply:

The blue wire might not be for the brakes and it could also be spliced to a different color wire somewhere that is unseen. The easiest way to determine the function of the wire would be to apply 12 volt power to it (by touching the wire to a positive battery terminal) and see what powers on. Be careful not to touch the copper wiring with your bare hands.

You might want to consider a junction box such as # 38656 which will make troubleshooting and identifying wire functions easier in the future. For new wiring we have # DW04914-1 sold by the foot.

expert reply by: Michael H