mpcarr,
Well Sir, for some odd reason, folks have tendency to panic when it comes to "tying" into the factory Jeep wiring for lights. I have no idea why. You can't get much simpler. You see, ALL the light wires pass right by the left knee of the driver, just under the door sill. We've towed (7) different Jeep Wranglers all over the U.S. and wired the stock tail light bulbs to work with the RV. We did that for over 25 years of Jeeping and they always worked perfect.
Absolutely NEVER had any issues what so ever. It's very easy. And, you don't have to run the wires from the coach all the way to the back of the Jeep. You simply remove the bulk of wires to a workable space along side the door sill. Then, you find the right turn, the left turn, and the running light wire. You then "T" into them with a clean solder joint and tape, DONE!
But, yes the diodes will have to be used so the signal from the coach does not travel down stream to the steering column and get the electrical system confused. I don't use those fancy Diode kits from the big suppliers like Camping World, E-trailer.com and others. I have used the $3.00 pack of diodes from Radio Shack and they're rated for way higher amp and voltage anyway so, I've always been way over protected.
Once you're done, your lights will work as they're supposed to. Now, as for your third brake light. No, there is no LEGAL requirement for it to be activated when the vehicle is being towed. I set mine up to be activated in my 2011 Honda CRV simply because it was easy to do so. The reason it was easy on the CRV was because that car has "Amber" turn signals which are totally separate from the brake light system. But, on a "two-filament" system, such as a Jeep, the third brake light is a totally separate system from the normal brake lights. So, to activate it with the wiring from the coach, would take intricate wiring.
Anyway, do as you like. There's no need to panic when it comes to tying into the factory wiring. It's wiring, not the plague. Simply strip some insulation, wrap your new signal wire from the coach, solder it, wrap it up with tape nice and tight, DONE. Put all the wires back under the door sill and, that's it. Your choice. Good luck how ever you do it.
Scott
P.S. Yes, if you add an auxiliary braking system like say, the Ready Brake, the Jeep brake lights will be activated when the Jeeps brakes are applied. Now you'll have two conflicting signals going to the tail lights. So, my simple remedy was to cut the brake light signal wire from the brake switch on the Jeep, run it to the door jamb where, I installed a micro-toggle switch, double throw.
On one side of the switch, I ran a wire right back down to the place where I cut it and tied it onto the cut wire. On the other side of the switch, I ran that wire, all the way to the front of the Jeep, the through the Pig tail, and all the way to the dash on on the motor home. Now, When towing the Jeep, I simply flip the switch so the signal from the jeeps brake switch is sent to the dash on the motor home where it lights a tiny LED, telling me the brakes are being applied in the Jeep.
When driving the jeep, we flip the switch so the signal from the Jeeps brake switch travels as normal to the jeeps brake lights.
Scott
Scott and Karla SDFD RETIRED2004 Itasca Horizon, 36GD Slate Blue 330 CAT
2011 GMC Sierra 1500 Ext Cab 4x4 Toad
2008 Caliente Red LVL II GL 1800 Goldwing KI60ND