JLUR battery flatlining when flat towing

[CoolTech]

I have found that the 12 volt charge line from the RV just does not provide enough for these newer vehicles with their power draw.

Newer vehicles - properly wired for towing, do NOT consume any more power than older vehicles when towing. To wit, a newer vehicle can sit parked for a couple of months or more - just like an older vehicle and then fire right up. Power for the lights (brake, turn signal, and marker) will always come from the tow vehicle via the installed harness. An aux braking system may or may not use the towed vehicle's battery for power and if it does, then a charging system needs to be sized to offset this draw.

As has been discussed previously (ad nauseum?) in this thread is that it is important that the towed vehicle remains in a sleep (low-power draw) state. In the case of the 2018+ Wrangler and Gladiators, ANY harness attempt to illuminate a rear light (brake/turn or marker) will cause the Jeep to wake-up IF AND ONLY IF that Jeep is equipped with factory rear LED lights. So, yes, a higher current Toad Charger may be able to overcome the current draw of one of the Jeeps that is not in sleep-state but this is addressing a symptom where it may be better to address the actual problem (not allowing the Jeep to wake up).

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[gm920]

Newer vehicles - properly wired for towing, do NOT consume any more power than older vehicles when towing. To wit, a newer vehicle can sit parked for a couple of months or more - just like an older vehicle and then fire right up. Power for the lights (brake, turn signal, and marker) will always come from the tow vehicle via the installed harness. An aux braking system may or may not use the towed vehicle's battery for power and if it does, then a charging system needs to be sized to offset this draw.

As has been discussed previously (ad nauseum?) in this thread is that it is important that the towed vehicle remains in a sleep (low-power draw) state. In the case of the 2018+ Wrangler and Gladiators, ANY harness attempt to illuminate a rear light (brake/turn or marker) will cause the Jeep to wake-up IF AND ONLY IF that Jeep is equipped with factory rear LED lights. So, yes, a higher current Toad Charger may be able to overcome the current draw of one of the Jeeps that is not in sleep-state but this is addressing a symptom where it may be better to address the actual problem (not allowing the Jeep to wake up).

Great idea, has anyone tried removing Fuse F22 (ECM/PCM/MGU WAKE UP/PPU WAKE UP) when towing? Any thought as to a possible downside?

 

[CoolTech]

Great idea, has anyone tried removing Fuse F22 (ECM/PCM/MGU WAKE UP/PPU WAKE UP) when towing? Any thought as to a possible downside?

Hi Gary, that is a good idea to explore. If it prevents the ECU from waking up, it is a straighforward solution. If, alternatively it disconnects power to the ECU and some things are reset (smog monitors, etc.), then maybe not worth it.

We DO have a solution that DOES work to keep these rear LED-light equipped vehicles in a Sleep-state. This solution will work with ALL tow harnesses and insures the Jeep remains asleep and in low-power mode.

Battery Drain Fix

 

[ekim]

Won't disconnecting pin 8 to the rear lights when towing work?

 

[CoolTech]

Won't disconnecting pin 8 to the rear lights when towing work?

Hi Mike, yes, absolutely this will work - but it isn't very pragmatic, right? Each time you tow, you need to remove the lights, pull apart the connector, and remove pin 8. Repeat for opposite side. Arrive at a location and do everything again in reverse order. Get ready to leave, do it all again.... and so on.

Essentially, our kit is is doing this with a switch.

Pin 8 is what the the BCM is looking at to see if a rear (LED) light has failed. If you leave Pin 8 disconnected, the BCM will display a warning on your dash that a rear light is out.

 

[ekim]

Hi Mike, yes, absolutely this will work - but it isn't very pragmatic, right?

I agree. Seems like this can be automated with a relay or like your excellent solution - with a switch.

 

[JimN]

I'm towing my JLUR behind a 35' gas-powered Class A. I'm using a Blue Ox baseplate, tow bar and umbilical but a Roadmaster Invisibrake. I also use the additional Roadmaster wiring kit that illuminates a red light RMI on my dash when I press the brake on the motorhome to indicate that the Jeep brakes are also being applied. The Jeep has Push-to-Start and automatic transmission.

Three times last summer the Jeep battery was drained when I drove the motorhome for more than one day without unhooking and driving the Jeep. At first, I thought I might have left the ignition in ACC, and it was a user error. After the second time, I made a point of starting the Jeep and letting it idle for 5 minutes before towing it each day, but the battery died again after towing it four days in a row.

Roadmaster says they have another wiring kit I can buy to provide a trickle charge to the Jeep when I'm driving, but they said I needed to disconnect it when I'm parked overnight or it might drain the motorhome battery! Another RV owner suggested a solar charger to provide the trickle charge.

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 experienced this last year for the first time. It was also the first time we went any distance or towed two days in a row without driving the jeep. It seems that even though your Jeep is OFF, when the brake peddle is activated, it triggers the Jeep to awaken. When this happens, it stays up for a while and eventually if this happens enough, you flat line. The simple fix is to install a chargeline. In order to prevent back flow or overcharge, the RVI Toad Charger is a good option at $95. You do not need to buy their control. Unfortunately the monitoring functions, although Bluetooth, do not work with a phone, there is currently no APP. I suppose this it to encourage the sale of their full system. If you are running a 'Suitcase' brake that connects to Toad for power, you definitely need a charge line. I learned that the hard way with my old Liberty behind my first Itasca. The installer did not provide a charge line. Got to Tulsa, from NJ and spent the one free day I had scrounging parts and crawling under both vehicles to add a line. I could go about 4 hours, no problem, much more and I had to jump the Jeep to get it up and running. On the newer Jeeps, with an AIrForce One, you might be able to install a kill switch on the brake light switch in the Jeep, but I am not sure if that would work, tehre could be other causes for the wake up.

 

[CoolTech]

Just to be clear about what causes the Jeep to become awake and consuming power:

Note: This occurs on any Jeep Wrangler or Gladiator that has the REAR OEM LED light option.

The activation of any of the rear lights by a towing harness - regardless of manufacturer/brand will cause the Jeep to come out of sleep mode. This includes the brake lights/turn signals and the running lights.

There are 3 ways to circumvent this problem so that it does not drain your battery;

1. You can install a high-quality battery charger such as the RVi Towed Charger Plus. This will not keep the Jeep from waking up but the charge function should offset the current draw occurring because the Jeep is awake.

2. You can disconnect the fault sense wire from both the left and right rear lights each time you tow. The fault sense wire is what is carrying back a 12v signal to the BCM and causing the Jeep to wake-up. This is an OK solution if you do not tow that often but it is kind of a PITA because you need to re-connect the wire when you are not towing - or you will get a "bulb out" message on your dash display.

3. We have a Battery Drain Fix on our website. Essentially it is just a switch that automates what you can do manually in Step 2, above. This fix is almost trivial to install if you are installing at the same time as our tow harness. Note that the fix WILL work with any tow harness - including MOPAR's own harness solution.... it is just easier to install when installed with our harness because you are in the same area making similar connections.

 

[Al G]

I experienced this last year for the first time. It was also the first time we went any distance or towed two days in a row without driving the jeep. It seems that even though your Jeep is OFF, when the brake peddle is activated, it triggers the Jeep to awaken. When this happens, it stays up for a while and eventually if this happens enough, you flat line. The simple fix is to install a chargeline. In order to prevent back flow or overcharge, the RVI Toad Charger is a good option at $95. You do not need to buy their control. Unfortunately the monitoring functions, although Bluetooth, do not work with a phone, there is currently no APP. I suppose this it to encourage the sale of their full system. If you are running a 'Suitcase' brake that connects to Toad for power, you definitely need a charge line. I learned that the hard way with my old Liberty behind my first Itasca. The installer did not provide a charge line. Got to Tulsa, from NJ and spent the one free day I had scrounging parts and crawling under both vehicles to add a line. I could go about 4 hours, no problem, much more and I had to jump the Jeep to get it up and running. On the newer Jeeps, with an AIrForce One, you might be able to install a kill switch on the brake light switch in the Jeep, but I am not sure if that would work, tehre could be other causes for the wake up.

You might want to read the entire thread.

 

[RubiBlueJLU]

Wow, lots of discussion since my last post/read.
Just to follow up on my posts……
2021 JLURD with LED lighting package. Tail light sensor wires disconnected.
No charge line for battery.

We have towed the Jeep for over 2700 miles over the last 4 months. Longest tow was was 895 miles (yes, I am keeping track) over a 3-day period.

NO battery/power/flatline issues.
Jeep does NOt wake up with braking/blinkers.

???

 

[Kraxler]

Does anyone know what pin to use with the MOPAR tow harness on he Jeep side to get 12 volts from the RV to the Jeep? Part number, Amazon link or anything else. Thanks.

 

[Gaffer]

Wow, lots of discussion since my last post/read.
Just to follow up on my posts……
2021 JLURD with LED lighting package. Tail light sensor wires disconnected.
No charge line for battery.

We have towed the Jeep for over 2700 miles over the last 4 months. Longest tow was was 895 miles (yes, I am keeping track) over a 3-day period.

NO battery/power/flatline issues.
Jeep does NOt wake up with braking/blinkers.

???

What are you using for a brake activator?

 

[Kraxler]

I’m using the ready brute manual brake activation. A steel cable pulls on the brake pedal. That is pulled by something similar to a uhaul surge brake system.

 

[RubiBlueJLU]

What are you using for a brake activator?

I use a ready brute style (older model) cable braking system. Uses no power. Inertia activated through the tow bar/receiver.

I also have a “brakes activated” switch installed in the Jeep. Wired to an led on the dash of my Rv. It pulls its power from the Rv. Let’s me know when the Jeeps brake pedal is activated.

 

[RubiBlueJLU]

Does anyone know what pin to use with the MOPAR tow harness on he Jeep side to get 12 volts from the RV to the Jeep? Part number, Amazon link or anything else. Thanks.

Here is a wiring diagram
The wiring is standardized

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