How to Determine What the Orange Wire of Trailer Wiring Circuit is on Trailer with 9-Way

Updated 09/04/2014 | Published 09/02/2014

Question:

I recently rewired my 1985 alpenlite 5th wheel. It had a Pollak 9-wire plug with the grey wire disconnected. After connecting all of the wires, all of the lights worked as did the brakes, however there was an orange wire on the old plug but none on the new plug. What was the old orange wire used for and should I connect it from the trailer side to one of the other wires in the new plug?

asked by: Richard P

Expert Reply:

The colors of the wires used for wiring up a trailer can vary widely among trailer manufacturers. Especially on a trailer as old as yours where someone could have rewired the connector with whatever wire was convenient.

To determine the function of the wire you can trace it back to see where it terminates or you can use a jumper wire from the positive post of a vehicle battery to put 12 volts on that wire to see what circuit activates.

Typically on a trailer with a 9-way installed the circuit with an orange wire is Reefer (tag) or Stop.

expert reply by: Jameson C