JLUR battery flatlining when flat towing

lagunajim

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Does anyone have any thoughts or suggestions? I'd like an idiot-proof way to make sure the Jeep battery stays charged and I don't need to do anything special when I'm towing multiple days. In your response, please keep in mind that I know more about how the systems work in my motorhome than I do about how a car works under the hood!
I towed a JK behind my Class A for 4 years. There was a lead in the interconnect between the vehicles that tied the 12V from the motorhome to the 12V in the Jeep. This lead was only hot when the motorhome ignition was turned on.

That solves your "drain the moho" battery possibility when leaving the vehicles connected overnight or for days, yet still powers the braking system in the Jeep from the moho during towing.

My moho was on a Ford F-53 chassis, and I think one of the leads in the rear towing "harness" was a Ford factory harness wire triggered by the ignition as described above.

Simple :)





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Thanks for the discussion. I had the RVi Towed Vehicle Charger installed earlier this week. I'm heading out on an RV trip on Monday and will be towing the Jeep for three days straight until I get to my destination on Wednesday, the Albuquerque Balloon Fiesta. Since it is a big city and I can get AAA to come charge the Jeep battery if it's dead when I arrive, I plan to set the transfer case to Neutral, the gear shift to Park (as I've been doing all summer) and see if the new RVi Charger does what it's supposed to do without any intervention from me (no disconnecting the umbilical, no starting the Jeep each day to let the engine idle, etc).

For the response that hinted about disconnecting the wire around the brake, that's not what I want to do. The whole idea is that I hoop up the Jeep, drive the RV for one or more days, then disconnect the Jeep and have it start. If you haven't driven an RV, there are a lot of details to manage. I don't want to add any more details for the Jeep.

The RVi charger was wired into the socket for the umbilical that I already use, so there isn't anything additional for me to do. I hope!
Bad news. I towed my JLUR for three days to Albuquerque. The battery on the Jeep was completely dead (no lights on the dash at all). The RV owner parked next to me graciously used his SUV to jump the Jeep. On the way home, I started the Jeep twice. When I got home, there was a little bit of battery power, but not enough to start the engine!
I'm checking with Winnebago to make sure that the wiring in the connection on the RV was the correct pin.
 

lagunajim

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Did you not find my post about connecting the 12V from the motorhome to the 12V of the Jeep via the umbilical useful?

I really think that's the simple answer you're looking for. It's Post # 17 above.

It is literally impossible for the Jeep battery to drain under this wiring configuration, and no chargers or other equipment is used.
 

CoolTech

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This is an informative thread for many current and future Wrangler JL "toad" users. As many of you know, we make a custom toad wiring kit for the Wrangler JL so that the towing vehicle has the opportunity to control the Jeep's parking, turn, and brake lights. The alternative to our harness is a "universal" diode-based kit, but our kit; 1) has fewer connections; 2) all connections are made within the interior of the Jeep; 3) provides full 12v to the lights (whereas all diodes systems rob power); 4) our solution is 100% PHYSICALLY isolated from the Jeep electronics and computers so there is never a chance of back-feeding, etc.

But, let's discuss the battery "draw" problem from the original post. For the Jeep's lights - be it our system or a universal diode system, all of the power from the lights comes from the tow vehicle. As such, if you implement a system that just control's the Jeep's lights, then you will never have a problem with draining the Jeep's battery. However, many people elect to install an auxiliary brake controller inside the Jeep. These systems apply the Jeep's brake pedal when the tow vehicle brakes and the Jeep helps in applying stopping power. In nearly all cases, these aux braking devices utilize the Jeep's battery to function. As such, these kits when used over a period of a couple of hours or more, can deplete the Jeep's battery. So, if you plan to use an aux braking device, you should install a device that continuously charges the Jeep's battery as you tow. The aforementioned RVi Towed Battery device is an excellent product for this. For a clean install, owners should consider using a 6-pin umbilical cord and socket so the 4 light wires (left, right, parking, and ground) can also have a 12V charge wire within the same harness. In other words, only a single (6-wire) umbilical cord connection needs to be made. Note that we sell a "Deluxe" JL wiring kit that includes the RVi Towed Brake component, a 6-pin socket and a 6-wire coiled umbilical cord for this specific purpose.

https://www.cooltechllc.com/2018-je...harness-kit.html#/69-jl_tow_harness_kit-basic
 
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PBJ2

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The RVI charger has a red light on the side that indicates it is charging. If you plug the umbilical into the MH, start it, open the hood on the Jeep and look at the RVI charger, you should be able to tell if it is charging.
 
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I towed a JK behind my Class A for 4 years. There was a lead in the interconnect between the vehicles that tied the 12V from the motorhome to the 12V in the Jeep. This lead was only hot when the motorhome ignition was turned on.

That solves your "drain the moho" battery possibility when leaving the vehicles connected overnight or for days, yet still powers the braking system in the Jeep from the moho during towing.

My moho was on a Ford F-53 chassis, and I think one of the leads in the rear towing "harness" was a Ford factory harness wire triggered by the ignition as described above.

Simple :)
So, here's the solution. After a LOT of double and triple checking of the wiring from the motorhome to the umbilical and into the Jeep, all the wiring was correct and in working order.

The problem was in the Owner's Manual of the Roadmaster Invisi-brake, the passive braking system that applies the brakes on the Jeep when I press on the brake in the motorhome. The Invisi-brake has its own trickle charge, but it's only active when the motorhome's running lights are on. I drive 95% of the time during the day. Whenever the motorhome engine is turned on, the headlights are on. What I didn't realize was that I actually had to turn the headlight switch in the motorhome one click to turn on the running lights whenever I'm towing.

Two weeks ago, I took a 5-day trip and planned to keep the Jeep attached for the last two days of towing. With the running lights on while driving, after the first two days, the Jeep started each time I disconnected. After towing two days home, the Jeep started, but I received a message on the dash that some auxiliary systems would be unavailable until I ran the Jeep long enough for the battery to re-charge itself. I didn't get that message after just one day of towing. Now, I leave the dash computer on the battery charge screen, so that I know immediately how much charge is on the Jeep battery when I'm starting the Jeep after disconnecting.

I had the RVi Towed Vehicle Charger installed before the trip to Albuquerque in October, but it wasn't strong enough to keep the Jeep battery charged over the three-day tow without the MH running lights also being on. Roadmaster said that there's no reason why the RVI device needs to be removed, so I'm leaving it installed for now.

I'm planning my trip to Alaska and will be driving 3- to 4-days at a time without needing to disconnect the Jeep. I'll check after two to three days to see how much charge is left on the Jeep battery.
 

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If I'm reading this correctly you have 2 battery chargers on and still can't keep the battery charged. It's hard for me to believe your system takes more out of the battery than two chargers can put in. I would have the Jeep battery load tested and if that isn't it start looking for other power drains. Might also check the voltage into your chargers.
 

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Question. I just set my 2019 jl up to flat tow. Air Force one and blue ox avail. I am getting ready to us and when everything is set up the display in cluster and main radio/Nav display is on. Including radio. I can turn off large display but small one stays on. Is that normal?
 

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Question. I just set my 2019 jl up to flat tow. Air Force one and blue ox avail. I am getting ready to us and when everything is set up the display in cluster and main radio/Nav display is on. Including radio. I can turn off large display but small one stays on. Is that normal?
Kirk - The way I read your question, it seems like you have the vehicle ignition set to "On". I am in the same boat as you - about to start flat towing, but from my research (in the Owners Manual), it looks to me like the ignition should be "Off" when towing, and if that is the case, all displays would be off. I have attached the relevant pages from the Owners Manual (p373 and 374 in my version of the Manual). In Step 10, the ignition goes to "Off" and there is nothing after that step that would put it in any position other than "Off".
Like I said, I have no experience in flat towing yet, so would love it if a pro could chime in here and confirm. Thanks

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Screen Shot 2019-03-03 at 7.45.04 AM.png
 

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Kirk - The way I read your question, it seems like you have the vehicle ignition set to "On". I am in the same boat as you - about to start flat towing, but from my research (in the Owners Manual), it looks to me like the ignition should be "Off" when towing, and if that is the case, all displays would be off. I have attached the relevant pages from the Owners Manual (p373 and 374 in my version of the Manual). In Step 10, the ignition goes to "Off" and there is nothing after that step that would put it in any position other than "Off".
Like I said, I have no experience in flat towing yet, so would love it if a pro could chime in here and confirm. Thanks

Screen Shot 2019-03-03 at 7.51.04 AM.png


Screen Shot 2019-03-03 at 7.45.04 AM.png
Thank you for the response. My jl has the push button start. I typically push it to turn it off. I wonder if there is another step I need to take to put it into off.
 

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Thank you for the response. My jl has the push button start. I typically push it to turn it off. I wonder if there is another step I need to take to put it into off.
I also have the Push Button start and when I press it for Off, the small display stays on, but only for about 30 seconds, then goes off.
 
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I also have the Push Button start and when I press it for Off, the small display stays on, but only for about 30 seconds, then goes off.
The length of time the small screen stays on is adjustable via the Jeep control settings.

The Jeep ABSOLUTELY must be OFF when you are finished putting the transfer case in Neutral and the transmission in Park. I printed the two pages that were displayed above when I started towing in May, 2018. The pages stay in the glove box and I ALWAYS refer to them when I'm connecting and disconnecting.

If you find that your ACC is on, then re-start the Jeep engine and turn it off until the engine is off. My radio is set to stay on for 30 seconds after turning off the engine, or until I open the driver's door.

The biggest problem that I had initially was that the transfer case lever was extremely difficult to move to/from Neutral. Sometimes, I have to go thru the steps 2-3 times until I can get the transfer case into neutral fairly easily. I think the trick is to never press the brake pedal after you start the engine.

Read your Air Force One owner's manual to see if you need to have the RV running lights on to trickle charge the Jeep battery.

Please let us know how the Jeep battery does after towing for multiple days without disconnecting and running the Jeep, Did the Jeep start right up? Did you get the message on the screen above the steering column that indicated that some auxiliary features would not be available until the Jeep battery has had a chance to fully re-charge itself?
 

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I have what appears to be exactly the same problem though I think my auxiliary braking system is the Air Force One or something like that. On long tows, I run into starting problems with the 2018 JL Sahara and what's particularly weird is if I just walk away from the Jeep for like 40 minutes, it starts right up. It's almost as though one battery is charging the other while it sits there. I don't know if my 2019 Tiffin 32SA has a running lights setting. I do know I tend to use the headlights rarely (rain, very early driving, and construction zones) and on longer tows (closer to 400 miles and up or consecutive days of towing without driving the Jeep) I get a message about auxiliary switches not working and charging and sometimes dead though the dash works normally and there's no tick tick tick from a meh battery. It's driving me crazy. Jeep found nothing wrong with the Wrangler's electrical system and this has NEVER happened in the over 18,000 miles of non towing. Starting has been an issue 4 times after towing and the message on 3-4 other occasions after roughly 30-35 long tows so far. Dealer of course who installed the towing stuff wants to blame Jeep but odds are it's something about this double battery system with one battery charging the other just enough after sitting for awhile and it's the trickle charging system that's part of the auxiliary braking. I'm ready to give up RVing over this cause it's bad enough with little odds and ends crap from the shitty way they build RV's, even Tiffins. I'm about to schedule picking up the RV from routine service after a pair of big trips where they winterized, serviced stuff, warranty stuff. I brought this up when I originally brought it to them 2 weeks ago and I'd love to point them into the right direction while everything is still under the warranty. Not to mention 2 hours each way from home.


So, here's the solution. After a LOT of double and triple checking of the wiring from the motorhome to the umbilical and into the Jeep, all the wiring was correct and in working order.

The problem was in the Owner's Manual of the Roadmaster Invisi-brake, the passive braking system that applies the brakes on the Jeep when I press on the brake in the motorhome. The Invisi-brake has its own trickle charge, but it's only active when the motorhome's running lights are on. I drive 95% of the time during the day. Whenever the motorhome engine is turned on, the headlights are on. What I didn't realize was that I actually had to turn the headlight switch in the motorhome one click to turn on the running lights whenever I'm towing.

Two weeks ago, I took a 5-day trip and planned to keep the Jeep attached for the last two days of towing. With the running lights on while driving, after the first two days, the Jeep started each time I disconnected. After towing two days home, the Jeep started, but I received a message on the dash that some auxiliary systems would be unavailable until I ran the Jeep long enough for the battery to re-charge itself. I didn't get that message after just one day of towing. Now, I leave the dash computer on the battery charge screen, so that I know immediately how much charge is on the Jeep battery when I'm starting the Jeep after disconnecting.

I had the RVi Towed Vehicle Charger installed before the trip to Albuquerque in October, but it wasn't strong enough to keep the Jeep battery charged over the three-day tow without the MH running lights also being on. Roadmaster said that there's no reason why the RVI device needs to be removed, so I'm leaving it installed for now.

I'm planning my trip to Alaska and will be driving 3- to 4-days at a time without needing to disconnect the Jeep. I'll check after two to three days to see how much charge is left on the Jeep battery.
 

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Have them put a charging line from the rv to your jeep. I pull a 2018 Rubicon over 20000 miles with no problems . But I had them install a charge line from the start.
 

paulrubin3

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My understanding is that the auxilary braking system I have already includes that feature. It's part of what drove the price well over $4K.

Have them put a charging line from the rv to your jeep. I pull a 2018 Rubicon over 20000 miles with no problems . But I had them install a charge line from the start.
 

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