Trailer wiring plug

[sdf350arls]

I've searched and searched so sorry in advance if this is redundant, but I need some help.

I've got to replace my factory trailer plug setup on my 2001 F350 SC. I've bought a replacement 7/4 pin plug and mount and I've disconnected my old plug. On the truck side of the OEM harness there is a plug that is used so you don't have to splice wires. Problem is there is a black wire with a green stripe in the harness and I haven't the foggiest clue what it should connect to. On my new plug I have a purple wire that is indicated to be reverse (I assume back-up lighting). Is that what I should connect the odd black/green wire to?

Thanks in advance!
-Arlie

[Fordman6]

Yep, the black wire with the green stripe is back-up lights in your factory harness and would normally go to auxillary circuit (center pin) of your 7 way connector. Of course if you have no use for back-up lights on your trailer you can make the center pin anything you want, like an aux. hot 12 volt feed, etc.

[sdf350arls]

Cheers!
Exactly what I needed to know thanks!
-Arls

[sparvin]

Not just for reverse lights though. On my boat trailer, when I put it in reverse, that signals the brakes to let up so the trailer can back up, otherwise I have to turn a release lever on the trailer.