JLUR battery flatlining when flat towing

[Gaffer]

Well it looks like there are two options for flat tow lights.
1. Cooltech harness.
2. RV Tow Harness by Mopar without LED lights.
A third option would be if jeep deleted the LED tail lights as part of the RV Tow Harness.
I will wait to see how the RV Tow Harness works out. It might be an option for me as I don't plan to order the LED lighting package. I might go after market with front LED headlights only.

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[garykk]

OK, I had assumed that's why you asked. The electric pump will NOT activate in any circumstance until/unless the engine is running... which is a GOOD thing from a TOAD perspective.

Thanks

 

[jmait769]

…..The SECOND problem is that when the Jeep is awake, any aux brake system that moves the jeep's brake pedal will cause the Jeep to activate its rear lights. This becomes a problem when the tow vehicle has a blinker on. The Jeep's rear light will be blinking. But, if the tow vehicle has a turn signal on and brakes, the Jeep's activation of it's brake lights will override the blinking turn signal. For anyone behind you, the turn signal will no longer be blinking.

So, yes, rather than install our LED light fix, you could install a charging system to prevent the Jeep's battery from going dead. However, you will still have the brake/turn signal conflict mentioned above (assuming you have an aux brake system that moves the Jeep's brake pedal.)

I’m currently towing a 2020 JLUR with factory LED tail lights, Mopar wiring harness, Demco Air Force One (actuating cylinder depresses the towed Jeep’s brake pedal), no BLIS and I added the RVi towed battery charger after reading about it in this thread but did not have drain issues prior. This past weekend I decided to test the system for correct LED function (while towing) as has been discussed here to make sure it worked as it should.
First I checked the system making sure the actuating cylinder that pulls the Jeeps brake pedal was setup properly and fully pulled the pedal towards the firewall. Brake lights and turn signals were checked both with MH applied brakes and just turn signals. All good. I waited a 10 minute interval the a 20 minute internal and with the MH brakes applied - all brake lights and turn signals worked with no override of the Jeeps light system. I pushed the brake pedal from outside the Jeep with a broom stick with MH brakes applied and observed that all lights functioned properly. No override of the Jeeps lighting system. With no braking action from the MH, and waiting another 10 minutes, I noted that the only rear lights that came on when pushing the Jeep brake pedal with the broom stick was the third brake light. It did not activate the rear LED tail lights at all.
Went on a camping trip with another RVer and had him follow me on a 5 hour trip, which included highway and heavy stop and go traffic and at no time did the Jeep lights malfunction, flashed when required and had no brake/turn signal conflict. I may have missed this in the thread but what was the reason for brake/turn signal conflict for LED tail lights? Thanks!

Jay

 

[CoolTech]

Jay - thanks for the long write-up.

When the Jeep is asleep (low power mode) it cannot activate its left and right rear brake lights. This is good as the Jeep will not interfere with any light operations coming from the Motorhome.

The issue is that when the MOPAR Tow Harness (or any other harness) activates one of the Jeep's rear LED lights, there is a wire from the LED rear light circuit board the feeds back to the Body Control Module (BCM). Unfortunately, this feedback will cause the Jeep to "wake-up" and it is no longer in low-power sleep mode. In this state, the Jeep will consume battery power but you are offsetting that battery draw with your RVi Towed Brake.

However, another anomaly that you WILL have is that when the Jeep is awake, movement of the Jeep's brake pedal will cause the Jeep to activate its Left and Right rear brake lights. So, let's say that the MH is commanding a blinking Left turn signal. The Jeep's rear light is blinking. But now, with that light blinking, you step on the MH brake pedal which in turn pulls down the Jeep's brake pedal. Now the Jeep will send a constant 12v signal to both the Left and Right rear bulbs... but the MH is sending a blinking 12v signal to the Left bulb. The result is that the left bulb will no longer blink, but it will be constant-on because of the brake lights. (Note that the Jeep uses the SAME bulb and filament for both the brake and turn signal. The Jeep "manages" this in normal driving.... if you have a blinker on that side will blink brightly and the other side will be constant-bright.) But, when the MH is sending one signal (blinking) and the Jeep sends another signal (constant), the blinking function will be lost.

Hope that makes sense... it's not easy to explain.

 

[jmait769]

Jay - thanks for the long write-up.

When the Jeep is asleep (low power mode) it cannot activate its left and right rear brake lights. This is good as the Jeep will not interfere with any light operations coming from the Motorhome.

The issue is that when the MOPAR Tow Harness (or any other harness) activates one of the Jeep's rear LED lights, there is a wire from the LED rear light circuit board the feeds back to the Body Control Module (BCM). Unfortunately, this feedback will cause the Jeep to "wake-up" and it is no longer in low-power sleep mode. In this state, the Jeep will consume battery power but you are offsetting that battery draw with your RVi Towed Brake.

However, another anomaly that you WILL have is that when the Jeep is awake, movement of the Jeep's brake pedal will cause the Jeep to activate its Left and Right rear brake lights. So, let's say that the MH is commanding a blinking Left turn signal. The Jeep's rear light is blinking. But now, with that light blinking, you step on the MH brake pedal which in turn pulls down the Jeep's brake pedal. Now the Jeep will send a constant 12v signal to both the Left and Right rear bulbs... but the MH is sending a blinking 12v signal to the Left bulb. The result is that the left bulb will no longer blink, but it will be constant-on because of the brake lights. (Note that the Jeep uses the SAME bulb and filament for both the brake and turn signal. The Jeep "manages" this in normal driving.... if you have a blinker on that side will blink brightly and the other side will be constant-bright.) But, when the MH is sending one signal (blinking) and the Jeep sends another signal (constant), the blinking function will be lost.

Hope that makes sense... it's not easy to explain.

Not sure how you are testing this but this does not happen on my setup. All lights work as expected. The Jeep lights are in sync with the MH at all times both static and on the road. The actuation of the Jeep pedal does not cause any problems.

 

[CoolTech]

Not sure how you are testing this but this does not happen on my setup. All lights work as expected. The Jeep lights are in sync with the MH at all times both static and on the road. The actuation of the Jeep pedal does not cause any problems.

I'm just saying how it works.... If you do NOT have the LED rear brake lights, then the Jeep will stay asleep and will not activate its own lights with movement of the brake pedal. If the Jeep "wakes up", then its brake lights will work with the brake pedal... and since the Jeep has no idea that the MH may be blinking a light, it will send a constant 12v signal for the brake lights which effectively causes the blinking to stop.

 

[jmait769]

I'm just saying how it works.... If you do NOT have the LED rear brake lights, then the Jeep will stay asleep and will not activate its own lights with movement of the brake pedal. If the Jeep "wakes up", then its brake lights will work with the brake pedal... and since the Jeep has no idea that the MH may be blinking a light, it will send a constant 12v signal for the brake lights which effectively causes the blinking to stop.

I do have the LED brake lights.

I will add one more test that I did but left off to make my earlier post a little shorter. With the Jeep running, window down and not connected to MH I placed ignition into the off position and got out. Waited 10 and 20 minutes and pressed the brake with the broom stick. The brake lights did not illuminate and as far as I can tell stayed in sleep mode. With the Jeep connected to the MH and the MH running, Jeep ignition in the off position and window down I waited the 10 and 20 minute interval and pressed the Jeeps brake with the broom handle. Only light that came on was third brake light. MH brakes applied and all worked as I stated in my earlier post.

Now this is the test I performed on MY JLUR with LED brake lights so I can only go by that. My take is the third brake light illuminating tricks the BCM into thinking all is well and does not come out of the sleep state. I never had the battery drain as others have had but I did add the RVi charger as I already had their TPMS system.
Not trying to be argumentative here - just sharing how my Jeep behaves with the Mopar harness and LED brake lights

 

[CoolTech]

Not trying to be argumentative here - just sharing how my Jeep behaves with the Mopar harness and LED brake lights

I find your posts to be very constructive and helpful.

In your tests that you just described in your previous post, the Jeep is staying in sleep-mode which is good and everything will work normally. You haven't yet done anything that would wake-up the Jeep.

Next time you are connected to your Jeep (and bored out of your mind, lol) leave the Jeep's window down and do the broomstick test after 5 minutes. The rear left and right brake lights will not illuminate... just as you described.

But, now turn on the running lights in the MH - which will cause the running lights of the Jeep to come on. I'm saying that by doing this the Jeep will wake-up. If you do the broomstick test now, the Jeep WILL light up its brake lights because it is awake.

 

[jmait769]

I find your posts to be very constructive and helpful.

In your tests that you just described in your previous post, the Jeep is staying in sleep-mode which is good and everything will work normally. You haven't yet done anything that would wake-up the Jeep.

Next time you are connected to your Jeep (and bored out of your mind, lol) leave the Jeep's window down and do the broomstick test after 5 minutes. The rear left and right brake lights will not illuminate... just as you described.

But, now turn on the running lights in the MH - which will cause the running lights of the Jeep to come on. I'm saying that by doing this the Jeep will wake-up. If you do the broomstick test now, the Jeep WILL light up its brake lights because it is awake.

Ok I know while on my trip I described earlier we traveled in rain and all lights were on including marker lights and my friend did not note any problems with the MH/Jeep lighting system. However, I will do the test you described next time it is hooked up just to be sure.
The reason I’m checking my system frequently is more related to the MH and a recall Freightliner has for a Primary Distribution Modular (PDM) which controls rear brake lighting. More info here: https://www.freightwaves.com/news/t...3rd-recall-of-freightliner-custom-chassis/amp
Mine has been replaced as required by the recall but hard to test 100% unless you have someone follow you. Add the possibility the Jeep could be not be preforming as wired sure gets frustrating!

 

[CoolTech]

Ok I know while on my trip I described earlier we traveled in rain and all lights were on including marker lights and my friend did not note any problems with the MH/Jeep lighting system.

My assertion(s):

1. Key off, doors closed... if the Jeep is awake, the brake pedal will activate the Jeeps rear brake lights
2. Key off, doors closed, if the Jeep is in low-power sleep mode, the brake pedal will NOT activate the Jeep's rear brake lights.
3. ANY/ALL towed wire harnesses (including Mopar's) installed on a Jeep with OEM rear LED lights.... activation of a rear bulb by the tow vehicle will cause the Jeep to wake-up.
4. If the Jeep is awake and the towed vehicle is sending a pulsing 12v signal to a rear turn signal light on the Jeep and then the brake pedal is depressed (via an aux braking system), the Jeep will send a constant 12v signal the both rear lights (Jeep has no idea what tow vehicle is doing) and the result is that the light will no longer blink but will be constant on (brake light).
5. A friend following you will have to pay careful attention to a specific scenario. You turn on a turn signal while approaching a turn and then when you brake hard enough to turn on the brake lights, the turn signal will not blink until the brake pedal light is no longer engaged.

A more serious consequence of the towing harness waking up the Jeep is the elevated current draw of the Jeep when it is awake. By using the RVi Towed Charger, you are masking this problem by continuously charging the Jeep's battery.

 

[jmait769]

My assertion(s):

3. ANY/ALL towed wire harnesses (including Mopar's) installed on a Jeep with OEM rear LED lights.... activation of a rear bulb by the tow vehicle will cause the Jeep to wake-up.
4. If the Jeep is awake and the towed vehicle is sending a pulsing 12v signal to a rear turn signal light on the Jeep and then the brake pedal is depressed (via an aux braking system), the Jeep will send a constant 12v signal the both rear lights (Jeep has no idea what tow vehicle is doing) and the result is that the light will no longer blink but will be constant on (brake light).
5. A friend following you will have to pay careful attention to a specific scenario. You turn on a turn signal while approaching a turn and then when you brake hard enough to turn on the brake lights, the turn signal will not blink until the brake pedal light is no longer engaged.

A more serious consequence of the towing harness waking up the Jeep is the elevated current draw of the Jeep when it is awake. By using the RVi Towed Charger, you are masking this problem by continuously charging the Jeep's battery.

As I stated before I did not have the battery drain issue and towed the Jeep for a year without the RVi Towed Charger and had no battery drain issues.
I was not able to duplicate the wake up process on my Jeep, including turning on the MH running lights, unless I have the key/push button in the Acc or Run mode. How are you testing this to wake up the Jeep with the key in the off position with it connected to the MH? If this is a defect in all Jeeps with the LED lighting system you would think it would be easy to duplicate.
I cannot imagine a more thorough test of the lighting system then someone following you for hours and not detecting any anomalies. I’m confident this lighting issue you are talking about is not happening with my Jeep with LED lights and the Mopar harness.
I think the lighting defect is a more serious consequence of the towing harness waking up the Jeep and if this is happening on anyone’s Jeep after installing ANY tow harness I encourage you to report it to the NHTSA (nhtsa.gov) as it is a safety defect just like the Daimler recall on the Freightliner chassis.

 

[CoolTech]

If this is a defect in all Jeeps with the LED lighting system you would think it would be easy to duplicate.

Several owners have duplicated this problem and have documented it on this forum. Not sure why you cannot. There's a small chance that Jeep was able to correct with a firmware update to the BCM.

I cannot imagine a more thorough test of the lighting system then someone following you for hours and not detecting any anomalies.

I can't imagine a worse test/validation. The person following you would have no idea as to when the turn signal is on/off overlapping with the brake light. Now, if you had 2-way radios or phone communication, then you could get a real test. However, this testing maybe moot given your point above. If, in fact, you JL is staying asleep, then there would be no conflict as the Jeep would never be activating its own tail lights.

I think the lighting defect is a more serious consequence of the towing harness waking up the Jeep and if this is happening on anyone’s Jeep after installing ANY tow harness I encourage you to report it to the NHTSA (nhtsa.gov) as it is a safety defect just like the Daimler recall on the Freightliner chassis.

As I said, many have validated the behavior that I have described. However, I disagree with you about it being a safety issue - or an issue that NHTSA would be concerned with. The biggest consequence is owners having a drained battery upon arrival to their destination.

 

[jmait769]

Several owners have duplicated this problem and have documented it on this forum. Not sure why you cannot. There's a small chance that Jeep was able to correct with a firmware update to the BCM.

It makes it possible that it is not the Jeep itself at fault here.

I can't imagine a worse test/validation. The person following you would have no idea as to when the turn signal is on/off overlapping with the brake light. Now, if you had 2-way radios or phone communication, then you could get a real test. However, this testing maybe moot given your point above. If, in fact, you JL is staying asleep, then there would be no conflict as the Jeep would never be activating its own tail lights.

Full 2-way contact.

As I said, many have validated the behavior that I have described. However, I disagree with you about it being a safety issue - or an issue that NHTSA would be concerned with. The biggest consequence is owners having a drained battery upon arrival to their destination.

I would validate this myself before relying on others - just a lot of variables to consider like the actual harness installation, an inherent problem with the Jeep, MH wiring problems or procedural while connecting the Jeep to the MH. As far as a safety issue we will just have to agree to disagree on this.

 

[Skystak]

I have a cool tech original harness and AF1 brake in my JL. I talked to cool tech as my 2020 jl would lose power on my Florida to California trip in my newmar dutchstar. I think the newmar always has the lights on. The more stop and go and longer the trip the more likely I am to go dead Battery.

Soon this trip I was near them in California while traveling through. They went out of their way to get me the part and get this…they hand delivered the second switch kit which was awesome customer service in any day and age! And explained how to install. Which I did at the campsite. It’s two new wires to find but the install went smoothly. Have a long trip back east so we will see in real conditions any and all effects. I believe they figured it out. I have a 5000 mile test that has now started. Cool tech, props to you, real customer service! That’s how to do business. It’s truly appreciated.

 

[Twbrow]

We have a 2020 wrangler jl rubicon and are having the same issue. I ran a wire from the 7 pin jack plugged into the rv to power my patriot brake but I guess I should use it to charge my battery instead. Can I just run the hot wore to the battery with an inline 15amp fuse to charge the battery. We are on the road and will order a rvi toad charger when we get home.

On a side note after the battery died our backup camera isn't working.

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