extra break wire

[twowheelv]

I just converted the old ford trailer plug to the 7 pin all the fifth wheels use. I have an extral wire for the electric breaks. I verified this with a multi meter and the volatges are the same for the two wires at diffrent break controler positions. Does anyone know why I would have two? Looks stock.

[Freightrain]

Something is awry. What plug did it have before? My '96 had a constant 12v for lighting(inside trailer), maybe someone tapped into it?

[KVOM]

The center post is 12V auxilary. If it's another contact then I'd suspect a short or a wiring error. The brakes and the taillights are supposed to be on the same wire, but it's possible someone decided to split it into two separate wires.