For anyone purchasing a Jeep Wrangler JL - 2018 or newer to set up as a TOAD, particularly if you're updating from an older series Jeep Wrangler, I thought this might be helpful information -
I towed my 2015 Wrangler JK behind my motorhome. I had it set up with a Rockjock towplate and a Readybrute Elite II towbar. The JK was pretty easy to wire up for towing. I got a Hopkins plug and play wiring harness that went inline with the rear lights. In order to keep the Jeep lights from overriding the RV lights, for example having a turn signal on while braking, the Jeep could just illuminate the brake lights. I added a brake light disconnect kit which consisted of a relay that stopped the signal to the Jeep's lights by opening the circuit. It was installed on the cold side of the brake pedal switch.
I traded in the JK and bought a new 2020 JL. I kept the Readybrute Elite II towbar because it's got a built in surge brake system. Rockjock makes a towplate for the JL so I ordered one of them. Hopkins does not make a plug and play wiring harness for the JL, but Curt does so I ordered that. I needed a new brake cable kit for the towbar and ordered that. The brake cable attaches to the brake pedal arm and is threaded through a conduit to the front of the vehicle where a clevis or carabiner attaches to the surge brake line on the towbar. I also ordered the emergency break away kit that will apply the JL's brakes should the towbar fail or disconnect. This is another cable run in parallel with the operating brake cable. I got the two brake kits from NSA, they make the Readybrute tow bar. While I was at it I ordered the brake circuit disconnect kit with the relay. This is where things got interesting.
There are all the wiring diagrams for the JL's on the internet. I printed out the wiring diagram for the brake system and discovered that there's 3 wires in the brake system. Not as simple as the JK with it's single wire. I asked a question on the electronics section and learned that the brake switch on the JL is tied into the anti-lock brake system as it senses the amount of force applied to the pedal. Cutting one of those wires to install the relay would have been very bad - if you don't get anything else out of this post, don't cut the wires to the brake switch.
I did more research as I wanted to know how I could avoid having the JL's brake lights override the turn signal from the RV with the wiring harness I added. I learned (from etrailer.com and other members here) that the lights on the JL turn off after a few minutes and are not an issue. That was good to know, so that means no relay needed. The towbar surge brake activates the brakes on the JL by pulling on the cable which is attached to the brake pedal with the RV lights lighting up the JL's tail lights, brake lights and signal lights as needed. But I went one step farther on the JK which I wanted to do for the JL too. There is a small LED kit that I installed in the dashboard of my motorhome. When the brakes were applied on the JK the lead for the LED was attached to the cold side of the brake switch and would light up on the RV dash. That way I knew the brakes were on but more importantly that they were off while I was towing. If the brakes are on you're going to wear out the brakes on your TOAD really fast. I also added an LED flasher to the 3rd brake light on the JK, the center mounted light above the spare tire. I didn't want anyone rearending my while I was towing. When the brakes were applied the 3rd brake light would flash really quickly 3 times, then slower 3 times then stay on solid. You've probably seen these on motorcycles, they really get your attention. Some people hate them but I'd rather have them hate me than run into the rear of my Wrangler. To activate that light I cut the wire to the 3rd brake light and spliced in the flasher. To power it I ran a wire to the cold side of the brake switch before the relay so the 3rd brake light would still work when the JK's lights would not. It worked great, in fact it worked when I was just driving the JK around.
So I needed some way to activate the dash LED in the RV and the 3rd brake light on the JL. The good news is the JL 3rd brake light is wired identically to the JK, a single hot lead and a ground.
I found that Roadmaster makes a kit specifically for the JL that will let you light up your dash LED in the RV and in my case the 3rd brake light at the same time. The kit has a bracket that attaches under the dash with an existing bolt and nut in the dash framework. There is a simple brake switch that installs in the bracket then one wire to the JL's battery for power and the other wire through the wiring to the RV for the dash LED. I spliced the 3rd brake light line into the RV dash LED line it works perfectly. Even when the JL has been sitting long enough the for power to time out so the brake lights won't light up when the pedal is pressed the 3rd brake light does. No interference with the anti-lock brakes, simple system. I did have to run a wire from the flasher, which I mounted inside the tailgate, up to the engine compartment where I spliced it to the RV LED brake signal line. I could have added diodes and spliced into the plug and play RV harness in the rear of the JL but the wire works and itís less expensive. I also didnít want to start cutting into that wiring harness.
On the JK I had an extra wiring harness with 2 wires that plugged in the front of the JK for the RV dash LED. I got smarter with the JL setup. The RV has a standard 7 prong RV plug and I put a 6 prong round plug on the front of the JL. I attached the lead from the additional brake switch to the electric brake lug on the 6 round plug then on the RV I took the hot lead to the dash LED and attached that to the electric brake lug on the RV plug. Now when I plug in the single wiring harness it not only powers up the JL's brake, tail and signal lights but also the RV dash LED and the 3rd brake light on the JL.
Any questions, fire away.
Here's links to what I used:
Rockjock towbar: https://www.rockjock4x4.com/ce-9033jlp
Readybrute Elite II: https://www.readybrake.com/store/p28..._Elite_II.html
Curt tow harness:
Stop light switch/bracket: https://www.amazon.com/gp/product/B07GNNNXDG/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
3rd brake light flasher: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1