Hi everyone, this is my first post on the F150 Forum. I have a 2003, F150XL, 7700 w/164K mi., and I'm trying trying to replace the crusty, (factory?) 7 pin, (old style round pins), non-functioning trailer plug w/new plug. The wires in the (factory?) harness feeding the plug are blue, white, yellow, green, orange, and black w/green tracer. I've confirmed w/my test light what they all do except for the black w/green tracer. Please, can anyone explain it's purpose? There is an (I think aftermarket) Tekonsha trailer brake controller in cab. I will use the truck to tow a 16 ft. tandem axle utility trailer w/electric brakes.Thank you, Tim

 

Perhaps this will help.
TRAILER WIRING DIAGRA

 

It would probably help if you list which wires are doing what. Blue has usually been used for trailer brakes. I think at that vintage they would have been using the current 7 pin RV (Bargman) flat blade plug. So it's probably aftermarket connector connected to factory. Have you checked reverse?

 

 

Put ALL its details into your signature so you don't have to re-post it with each question, and we don't have to search, ask, or wait.Probably the 1 purpose for which you haven't already identified a wire.

But this diagram & its caption list most of the wire colors that Ford (& others) has used over the decades:

(phone app link)

 

Here you go.....bottom right connector C439a -> (BK/LG) Trailer tow connector (15A416), Reversing lamps, feed.

 

Thanks for all suggestions. I did not check reverse, I will do that. Here's what I concluded w/a test light, green = right turn/stop, yellow = left turn/stop, blue = trailer brake/stop, orange = constant hot, white = ground. I think by process of elimination that leaves running lights (parking lights) (?) I'm pretty sure I checked that, but I will check again. If the black w/grn trcr supplies the running lights, there might be a separate (possibly blown) fuse for the trailer wiring, or some spot where it's compromised.

 

Who sold off their child to the slave drawing society?

 

Thanks for the .pdf, the black w/grn trcr was reverse, and I found the parking lights supply broken upstream in the loom. I think it's brown w/wht trcr. It was trickier than I anticipated feeding the wires into the new plug housing and securing each in their proper spot, given the confined space, and the spring loaded dust cap adding difficulty. As always my cat was willing to help, but I needed extra set of hands, not quite paws.

 

The 12V black wire is usually thought of as the RV battery charge wire. It should be hot any time the engine is running.

The auxiliary (orange) wire is a 12V hot wire often called the trailer backup lights wire, but it can be wired to be hot only when the tow vehicle is in reverse gear (for trailer backup lights) or all the time when the engine is running. If wired to be hot 12V all the time (when he engine is running) then it's a true "auxiliary" 12V hot wire that could be used for anything for which you need constant 12V power. such as a camera or TPMS.