Note: This is technical wiring stuff and might not be of much interest to those who don’t have an RV and/or flat-tow a vehicle. I put it up here just to show some of the things we have to do to prepare and just in case someone else ever gets this wiring harness and can’t figure out why it doesn’t work.
I spent most of today running around getting pieces and fixing our towing connector on the RV. It wasn’t actually broken, it just wasn’t right.
This is our 7-way tow connector socket on the back of the RV. Whenever you’re towing something, it gets plugged into this. When you hit your brakes, turn signal or turn on your lights, it sends electricity through the appropriate “prong” and lights up whatever light is necessary on whatever you’re towing.
Since we got a new Jeep, we’ve had to prepare it to be “flat-towed” behind the RV. I took care of the physical stuff to hook it up to the RV hitch when I got the bumper done. I installed a special wiring harness from Jeep to take care of the electrical stuff. Unfortunately, when I plugged it into the RV I got nothing. No lights at all. I was just about to run back to Jeep crying like a little girl when I decided to test it on my step-father’s Chevy Avalance (he has the same 7-pin tow connector). It worked perfectly!
That meant that the Jeep wiring kit was okay (and I didn’t kill it when I installed it), but something was funky on our RV. I had to wait two days for any of the local trailer shops to get a 7-pin tester in before I could figure out what was going on. When I put the tester on, it showed that one line (which isn’t necessary for most towing applications) was dead. Here’s a quick description of the pins in the connector above:
1 – Ground (common return path)
2 – Left turn and brake light
3 – Tail and running lights
4 – 12 volt charging power
5 – Right turn and brake light
6 – Brake controller
7 – Reverse lights
Ours had everything except the brake controller wire (we don’t have a brake controller) and the 12 volt charging wire (pin 4). The brake controller is generally used for towing heavy trailers and it activates the brakes on the trailer when you hit the brakes on the RV. The 12 volt charging line is generally used for towing campers and it charges up the battery on the camper when you’re connected.
Unfortunately, Jeep decided to use the 12 volt charging line to “activate” the wiring harness that I just installed. No charging line, no lights. So, I got to spend most of the afternoon dissecting the socket and running a power line to one of our six batteries in the RV.
So, if you plan to flat-tow a newer JK model Jeep and you plan to get the wiring harness from Jeep to do so, there are some things you should know…
- The harness part number from Jeep is 82211156AB. You can find it on the Mopar Accessories site.
- Installing the harness is a serious pain. It’s not worth doing. Pay a dealership to do it. You have to remove body parts, pull up carpeting, drill big holes in the firewall and then fit a 2 inch grommet into a 1 inch hole… without crushing the wiring harness in the process.
- Get a 7-way tester if you plan to tow regularly… no telling when something will stop working, it’s a useful tool to have.
- Make sure the 12-volt charging line is active. It should light up immediately when you plug in the tester (it’s supposed to be constantly on).
- I don’t care what the description says, the harness does NOT include an “underhood battery disconnect”. Plan on getting a battery disconnect. If you don’t, the Jeep will rack up miles when flat-towed unless you disconnect the battery manually.
Oh, the numbers I used for the pins in the diagram aren’t “common”. If you’re going to wire up a connector or anything, check the diagram that comes with the connector. Don’t expect my number 3 pin to be the same as everyone else’s.