Not sure if there are other write ups for this but couldn't find anything great in my short search before I did mine. Actually did this like 2 months ago when we made a seat-of-the-pants purchase of a pop-up camper that had electric brakes. The purpose of this is a DIY, instead of just purchasing the mopar 7 pin wire harness, and or paying someone to do it.

Of course we know that the Wrangler has no provisions for a 7 pin connector. Very silly since most states require the brakes if your trailer weighs more than 3000 lbs, and the tow capacity is 3500 lbs.

First off I do have the 2012 JK U Sport with Max Tow. I purchased a 7 pin connector that had the 4 pin connector to plug into my existing 4 pin. In the future, I may just whack off the connector and splice it all in behind the bumper, so the 4 pin receptacle is always open.

First thing I had to do was run two wires from the back to the front. One wire for the brake controller, one wire for the 12v constant power. If you have reverse lights on your trailer, you'll want to run a third wire, however since I don't, and probably never will, I did not run that wire, and don't know where to tie it in to. I got some split loom tube just big enough for the (2) 12 gauge wires, and basically followed the driver’s side frame rail up to just before the wheel well trim and up to the engine bay. The brake controller (traditionally blue) wire can run right into the cab through the firewall (see the pics, this is the one part they got right; there is a nice big rubber grommet that you can punch through and run wires to and from the cab and engine bay). The constant 12v wire was run to a 40amp auto circuit breaker, and into the battery positive. The next wire runs from the battery positive, to a 20amp auto circuit breaker, through the firewall to power the brake controller.


Not the prettiest... I'll be cleaning that up in the near future.


The blue wire is going through the rubber hole in the firewall.

The brake controller is traditionally mounted near the driver so they can pull the oh shite handle if needed, and see the screen in case of errors or what have you. Exact angles differ based on the controller, so consult your manual for that. Not a lot of options in the Jeep cab however. The controller will need 4 wires hooked up for it to work properly. Many manufacturers have "plug and play" harnesses that just plug into the vehicles existing harness. Like was mentioned, the Jeep has no provisions like this, so you will have to do some splicing. One wire is hot (the wire we ran from the battery through the 20a circuit breaker), one is the blue wire from the 7 pin connector, the third is a ground, which I ran through the firewall to the nearest grounding stud in the engine bay, and the last wire gets wired to the brake line so the controller knows when the brakes are pressed. This wire is directly above the brake pedal, and is the white with tan stripe one; you will need an inline tap for this one, and is definitely awkward as there is not much room.
I use the Hayes G2 controller. Many people also love the P2 Prodigy, which I have no experience with, but the G2 we have in our two tow vehicles at work, and they all work great. The one odd thing you will see in my install/pics is the connector to make the controller removable. The G2 comes with a 4 conductor connector (as I think most do), which you are then supposed to buy the harness for the other end to plug into your vehicle. They also make bare wire ones which is what I should have used for the Jeep. Instead I didn’t have it when I was doing the install (same day I was picking up the camper), so I just crimped them together, and later put on a 4 conductor connector that we had in the shop laying around… way more intense then what’s needed, but it was free.



With a lot of help from my buddy who had the tools, we fabbed up a mounting bracket for the 7 pin connector which I then just screwed into the underside of the frame next to the existing 4 pin connector. I think that turned out pretty well. Only thing I want to change in the future is paint the screw heads black as I think they stand out in the back now...

I'm sure I probably missed something so please feel free to ask questions. Hope this helps others.





PS, on a related note to towing... I originally bought a "ball mount kit" that ended up being too short and I couldn't get the trailer onto the ball (the locking device on the trailer just hit the spare tire). The solution was just to get a longer ball mount, as apposed to a hitch extendeder, which, from my reading, cuts the tow capacity in half. The new one measures 12-1/4" from the pin hole to the center of the ball. Just an FYI as it is something I didn't think about until I went to hook the trailer up...

 

Nice write up thanks

 

Excellent timing! I was just considering the 7 pin harness vs. the 4 pin that came with my hitch. I wasn't sure how difficult it would be to add the additional wires, now I know.
Easy peasy.

 

Nice job! Basically looks like mine but I installed my 7-pin connector below the license plate, on the top of the bumper. I used a hole saw to cut a hole the exact size of the 7-pin and a small hole out the back side. I pulled the factory 4-way and it is "smushed" between the bumper and the frame rail. The 4-way is connected to the 7-pin. I have an adapter that goes from 7-pin to 4-way if I need to; however, the 4-way is built in. I can also unplug the 7-way from the factory 4-way and hook straight a trailer straight to the factory 4-way.

I'm glad I did it this way as I've bent the factory mount for the 4-way.



Oh, I did take the bumper off the rear to cut the holes after marking it for where it would be best.