I am currently installing a brake controller in my ’09 2500. I installed one in my old Ford 350 years ago and it appears to be much the same.
Mine (the controller) has four wires which are color coded. The truck came with a plug and pigtail (found in the glove box with instructions). The female plug is located just above the parking brake pedal. This links to the rear trailer plug so all the hard stuff is already done.
Finding a place to locate the controller was my problem. I’m short ( 5’6”), so by the time I get the seat up where I’m comfortable there is little knee room for the traditional mounting place (under the dash in front of one or the other knee). What I will be doing is just pushing the controller into that little cubby hole just above the radio. I have tried this and it is a snug enough fit that I think it will work out OK. I thought about pulling the dash and running the wiring up through the dash to this location. But, this would entail more dismantling than I wanted to do plus it would mean drilling holes and giving up that space.
I have made up a harness to route the wiring from the plug under the dash, down the channel by the left door sill, and under the driver’s seat. There it will come out through the hole in the carpet for the seat wiring and end in a plug. I am in the process of completing the harness from the controller that will plug into this harness when I am using the trailer.
Yes, when I am using the controller the harness will drape down in front of the radio to the floor. That would not be “clean” enough for some. It could also interfere with a passenger who was sitting in the middle front seat. For me, the pluses out weigh the minuses so I am choosing this option but it might not be acceptable for others. When I am not using the controller it will get unplugged and stored out of the way with only the plug from the front harness showing under the driver’s seat. I only offer it as one option.