Mopar Flat Tow Harness arrived

DwnSth

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Noob question for you in the know. I had the mopar flat tow harness installed along w tow harness. We just arrived in San Antonio and disconnected Moabee and battery was dead. Isn’t the harness supposed to keep the battery charged or at least use RV power for the lights? Not sure if I’m missing something or amiss.
Was only connected since Friday, today is Sunday.
The harness does not automatically charge. A separate charge cable is needed. There are several mentioned in this thread. Be sure to get one that has a automatic controller so when motorhome is shut down the controller will not allow feedback to the coach and drain the jeeps battery.





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hingedthinker

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The harness does not automatically charge. A separate charge cable is needed. There are several mentioned in this thread. Be sure to get one that has a automatic controller so when motorhome is shut down the controller will not allow feedback to the coach and drain the jeeps battery.
Thank you. $750 installed, I am disappointed that mopar failed this part of the equation and I have to spend more now.
 

MoJoe

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I just traveled 2488 miles, Jacksonville, Florida to Los Angeles with the Mopar Flat Tow Harness installed. Under normal circumstances you will not need a charge line, especially if you have LED taillights/turn signals. That is the only power draw. However, from experience, you must be sure the Jeep’s ignition is in the OFF position before you tow. If you go through the process of putting the transfer case in neutral, as called for in the owner’s manual, when you put the Jeep back in PARK, for some reason, the ignition switch will go to the ACC position. If you don’t cycle it to OFF you will arrive with a dead battery.
i drove the first 1,000 miles over 3 days, no problem, Jeep started right up. Apparently, that 3rd day after I started it, I inadvertently didn’t check the ignition switch position and arrived at the next campground 400 miles later and the Jeep was dead as a door nail. Jumped it and took it out for a drive to charge the battery. This time when I hooked back up and put it back in PARK I made sure the ignition was in the OFF position. No more problems for the next 1400 miles. Bit of a quirk in the system.
 

hingedthinker

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I just traveled 2488 miles, Jacksonville, Florida to Los Angeles with the Mopar Flat Tow Harness installed. Under normal circumstances you will not need a charge line, especially if you have LED taillights/turn signals. That is the only power draw. However, from experience, you must be sure the Jeep’s ignition is in the OFF position before you tow. If you go through the process of putting the transfer case in neutral, as called for in the owner’s manual, when you put the Jeep back in PARK, for some reason, the ignition switch will go to the ACC position. If you don’t cycle it to OFF you will arrive with a dead battery.
i drove the first 1,000 miles over 3 days, no problem, Jeep started right up. Apparently, that 3rd day after I started it, I inadvertently didn’t check the ignition switch position and arrived at the next campground 400 miles later and the Jeep was dead as a door nail. Jumped it and took it out for a drive to charge the battery. This time when I hooked back up and put it back in PARK I made sure the ignition was in the OFF position. No more problems for the next 1400 miles. Bit of a quirk in the system.
I suspected that may have been my problem as well. Thank you for the heads up.
 

MoJoe

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Yeah, I use a Demco Air Force One brake controller. So it only uses the air from the air brakes on my motorhome. Only 12v requirement is for the wireless indicator relay to the indicator light on the dash of my RV. That uses hardly any power and only when braking.
 

hingedthinker

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This should be on your checklist. 2019 moab. Thank you Mojoe
 

kevinfloats

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I ordered the Roadmaster diode wiring, but considering to return it and order the MOPAR wiring so I don't have to splice anything. I'm still waiting for my Jeep to arrive. Does anyone know the correct part number and/or a good place to buy this for the 2021 JLU? I've seen a few different part numbers in this thread.
 

MoJoe

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I ordered the Roadmaster diode wiring, but considering to return it and order the MOPAR wiring so I don't have to splice anything. I'm still waiting for my Jeep to arrive. Does anyone know the correct part number and/or a good place to buy this for the 2021 JLU? I've seen a few different part numbers in this thread.
Here ya’ go:

B5F61376-6A0F-41DE-899A-4DADD59961E6.png
 

RonLee

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I'm waiting on my JLU also and after following this thread and doing my own research, I ordered the Cool Tech wiring system. This is my first JLU, owned 4 JK's and used the Mopar harness on all of them, and loved it. For some reason Mopar sure changed the JL harness to a real mess in my opinion. The install on the Cool Tech System is easy compared to the Mopar harness. The splicing into a few wires is nothing to me, after all most of us do way more involved upgrades than this simple one. I'm also adding a Hopkins battery maintainer (#39332) just to be on the safe side (I really don't think it is necessary, but for a few bucks, why not).
 

MoJoe

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I'm waiting on my JLU also and after following this thread and doing my own research, I ordered the Cool Tech wiring system. This is my first JLU, owned 4 JK's and used the Mopar harness on all of them, and loved it. For some reason Mopar sure changed the JL harness to a real mess in my opinion. The install on the Cool Tech System is easy compared to the Mopar harness. The splicing into a few wires is nothing to me, after all most of us do way more involved upgrades than this simple one. I'm also adding a Hopkins battery maintainer (#39332) just to be on the safe side (I really don't think it is necessary, but for a few bucks, why not).
The only “mess” is the removal of the interior trim panels IMHO. Once that is done, it is “Plug and Play”. I like the MoPar harness because there is no splicing and the ECM recognizes that it has been installed and works accordingly. You are right that we all do some splicing to do the installation of certain accessories, however, on the new JL’s with the Auxillary Switch setup, Jeep has provided a lot of opportunity to wire accessories in without having to resort to splicing. Extra lighting, winches, etc. can all be wired direct. So, for me it was an easy decision to not have to splice into the taillight wiring for a flat tow system. Plus I don’t have the ugly 6-PIN plug sticking out the front of the Jeep. The MoPar plug is kind of hidden up behind the bumper. With Demco “Invisible” Tow Plate it makes for a pretty clean setup.

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hingedthinker

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Battery in the jeep died again on the way home from Guadelupe River. I had used it there so it charged. Guess I killed it. Going to invest in the charger.
 

MoJoe

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Battery in the jeep died again on the way home from Guadelupe River. I had used it there so it charged. Guess I killed it. Going to invest in the charger.
As someone said earlier in the thread, if you have a supplemental braking system that requires 12V to operate you made need a charge line.
 

gsuhm

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For anyone interested, I documented my install of this harness. I ended up going through the interior for the install, which went smooth. Although getting through the wiring bundle in the firewall was pretty scary! We also ended up cutting off their proprietary connector and using our own to integrate better with our Invisibrake.

 

DwnSth

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Bad wire on flat tow harness. After months of no problems, my left blinker stopped working when connected to the tow harness and RV. I've verified power from RV to my blue ox connector which is spliced into the original RV side of the tow harness. At the fuse connector junction box, I no longer have power on the red left blinker wire. Is there anyway to remove the wires from the jeep side connector piece or from the fuse junction box. I have no good way of testing the wire individually other than direct power on the connector pin does not show up on the fuse box side.
 

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