Ok, here's more information about my story than you care to know, but it will give context to how I got to the point that I may be able to help. I have a 2010 ford expedition el xlt. It came with the 4 flat and hitch. I searched for quite some time to find out what the difference was between my version and the heavy duty tow package. I called numerous dealers who supposedly looked up my VIN and all that, but couldn't answer my question. Finally I learned that the only difference was a 7 pin, heavy duty radiator, and heavy duty transmission cooler. Adding these things would up my tow capacity by almost 3k pounds. My axle ratio was the same, just those three differences. I found the blue electric brake wire for a 7 pin capped just behind my 4 pin connector. Unfortunately on my vehicle it wasn't just plug and play because I couldn't find a 12v lead (which brings me to this post--and hopefully some help). I searched all over the web trying to figure out where it could be. I read that people just run one from the battery, but wanted to make this as clean and factory as possible. I stumbled across some posts and after some poking around with the information I had, I found that there is a 12v wire that goes into a wiring harness under the hood near the back driver side part of the engine compartment, but it doesn't come out the other side of the wiring harness...so basically it was run into a wiring harness, but not run out of it on the other end. I went down to the dealer, got the proper size pin and brought the wire out the other end, ran it in under the vehicle and wired it into a 7 pin. Maybe your year is stopped at a different spot, but that is where I found mine. If you decide you want to see a picture of the harness I'm talking about, let me know and I can take one and figure out a way to get it to you.
Any chance I can get in saving someone the headache I went through to figure something out, I'm happy to help.
