Flat tow 2019 Jeep JLU

[Fat Boy]

I have recently set up my 2019 JLU for flat towing. This is my third experience towing Wranglers and for the most part was straight forward set up. My problem is with the brake light wiring. How do you stop the Jeep’s brake lights from coming on when the aux braking system is activated? The brake lights should only be activated / powered from the motorhome while towing.

All my tow hardware is Roadmaster and my aux brake system is Roadmasters Even Brake

[Lt Dan]

The only way I am aware of to stop the Jeep's brake lights from coming on when the pedal is pushed is to install a cutoff switch in the brake like wire. Be aware there are two switches on the pedal, one for the lower lights and one for the high mount third light. I assume you want to disconnect them because the braking system overrides the turn signals when it activates.

[Steve-W]

Roadmaster sells a brake light relay kit for that purpose. I used it on my 2019 Jeep Cherokee setup with the Invisibrake.

[Cousin Ed]

What's the problem with them coming on? They can't use too much power and an extra set of brake lights is an asset.

[Lt Dan]

Originally Posted by Cousin Ed

What's the problem with them coming on? They can't use too much power and an extra set of brake lights is an asset.

The problem is with a brake system that pulls or pushes the brake pedal the Jeeps brake lights override turn signals from the MH. That causes a constant signal to the light instead of blinking with the turn signal. With the override, the Jeeps brake and turn signal lights operate normally in sync with the motorhome's lights.

[Fat Boy]

Correct. I want the lights on the Jeep to be in sync with the lights on the motorhome. I wanted to avoid installing a brake light relay.

[FIRE UP]

Originally Posted by Cousin Ed

What's the problem with them coming on? They can't use too much power and an extra set of brake lights is an asset.

As I understand it, the OP is wanting to use his regular tail lights as toad lights. And, that's the way I've done it for a few dozen toads. I myself don't like adding bulbs, magnetic lights, light bars and all that other junk. I want my tail lights on my toad, to act identical when towing it, as they do when I'm driving it. Following drivers are aware of how they should work. Any other type of display, confuses your average driver.

Now, the problem is when one uses an auxiliary braking system, about 95% of the vehicles that are flat towed and are used as a toad, have the brake lights activated when the key is OFF. That means if something pulls or pushes on the brake pedal when it's being towed, it's own brake light switch will apply brake lighting to the tail lights.

If you have signals from your coach, going to the same bulbs, like turn signals, now you have what's called a conflicting condition. You have TWO DIFFERENT TYPES OF SIGNALS going to the same filament, at the same time. NOT GOOD! Sooooo, that's what a brake light relay is for. It's job, when wired correctly, is to not allow the Jeeps brake switch, to send a brake light signal to its tail lights, when the key is in the OFF position, as in when being towed.

But, when the key is in the ON position, as in when DRIVING IT, the relay allows the Jeeps brake light switch, to send its signal to the brake lights, just like it's supposed to. It takes a tad bit of time to correctly wire that relay but, you're done forever. You never have to worry about the conflicting signals again.

Hope this clears things up.
Scott

[Steve-W]

Originally Posted by FIRE UP

As I understand it, the OP is wanting to use his regular tail lights as toad lights. And, that's the way I've done it for a few dozen toads. I myself don't like adding bulbs, magnetic lights, light bars and all that other junk. I want my tail lights on my toad, to act identical when towing it, as they do when I'm driving it. Following drivers are aware of how they should work. Any other type of display, confuses your average driver.

Now, the problem is when one uses an auxiliary braking system, about 95% of the vehicles that are flat towed and are used as a toad, have the brake lights activated when the key is OFF. That means if something pulls or pushes on the brake pedal when it's being towed, it's own brake light switch will apply brake lighting to the tail lights.

If you have signals from your coach, going to the same bulbs, like turn signals, now you have what's called a conflicting condition. You have TWO DIFFERENT TYPES OF SIGNALS going to the same filament, at the same time. NOT GOOD! Sooooo, that's what a brake light relay is for. It's job, when wired correctly, is to not allow the Jeeps brake switch, to send a brake light signal to its tail lights, when the key is in the OFF position, as in when being towed.

But, when the key is in the ON position, as in when DRIVING IT, the relay allows the Jeeps brake light switch, to send its signal to the brake lights, just like it's supposed to. It takes a tad bit of time to correctly wire that relay but, you're done forever. You never have to worry about the conflicting signals again.

Hope this clears things up.
Scott

FIRE UP excellent description of the situation. What I did was use a brake light relay setup to activate from the TOAD's charge line from the coach, this way whenever the coach ignition is on the TOAD's internal brake pedal signal is defeated and the coaches signal operates the lights in unison with the coach. As you said one and done.
Roadmaster says to wire the relay to the running lights for activation but in my mind that requires an extra step and I typically don't keep the running lights on in clear daylight.

[Steve-W]

Originally Posted by Fat Boy

Correct. I want the lights on the Jeep to be in sync with the lights on the motorhome. I wanted to avoid installing a brake light relay.

In order to accomplish what you want (which is the correct way to wire the TOAD) you will need to install a brake light relay.

[CoolTech]

This is a valid discussion but moot for the op.

The 2019 JLU will enter a sleep state ~ 30 seconds after the last door is closed. In this sleep state, the brake lights will NOT activate. You can verify this by turning the jeep off with the driver's side window down. Exit the Jeep and close the door. Wait a couple of minutes. Stick a broom handle in through the open window and depress the brake pedal. No lights!

Regarding the wiring of the JL (2018+ Wranglers) and the JT (2019+ Gladiators), I would caution against the "universal" diode-based harnesses - especially if you have the LED lighting option. Each light at the rear of the Jeep has an additional wire back to the ECU called a fault-sense wire. Unlike conventional bulbs, the LED's need a small circuit to help detect a failed light. We have a harness specifically engineered for JL/JT Jeeps that physically isolates the increasingly complex Jeep wiring. We don't depend on diodes that are often made in China, a heat source, and a point of failure. Instead, we employ a switch to achieve PHYSICAL isolation - so that you can be assured that there is no potential for potentially harmful signals to get back to the Jeep's ECU or BCM (Body Control Module).

[MtCamper]

I have a JLUR that we tow twice a year. Montana to Yuma and back. We don't tow in between times so I'm not hooking/unhooking a bunch. I took a look at the wiring in the JL and decided I was way too dumb to alter anything without jeopardizing the warranty. Went to HF and got a pair of magnetic tow lights then looked around for a place to mount them. Just enough room on the rear quarter panel. Just went with a 4 pin pigtail off the lights of my fifth wheel. It's worked for us now for 2 1/2 round trips. They work independent of anything the Jeep does.

[wayfarer2021]

I will be buying a 2019+ jeep when my new Class C arrives. So based on this I do not need any kind of accessory relays. So if I use the Jeep Trailer Hitch Wiring Harness, which I believe is plug and play, what would be the advantage of the Cooltech system?

Thanks for the help.

Originally Posted by CoolTech

This is a valid discussion but moot for the op.

The 2019 JLU will enter a sleep state ~ 30 seconds after the last door is closed. In this sleep state, the brake lights will NOT activate. You can verify this by turning the jeep off with the driver's side window down. Exit the Jeep and close the door. Wait a couple of minutes. Stick a broom handle in through the open window and depress the brake pedal. No lights!

[RayandWendy]

Originally Posted by wayfarer2021

I will be buying a 2019+ jeep when my new Class C arrives. So based on this I do not need any kind of accessory relays. So if I use the Jeep Trailer Hitch Wiring Harness, which I believe is plug and play, what would be the advantage of the Cooltech system?

Thanks for the help.

The actual Mopar harness is plug and play. No switches, no cutting, just running the harness. It has relays built in. Works great on my 2018 JLU. I'll admit it's a little difficult to install if you already have a tow harness installed. They use the same runs.
Later ...
Ray

[CoolTech]

Originally Posted by wayfarer2021

So if I use the Jeep Trailer Hitch Wiring Harness, which I believe is plug and play, what would be the advantage of the Cooltech system?

Thanks for the help.

It is easy to confuse the two different harnesses. The trailer hitch wiring harness is a specific harness which enables the Jeep to tow a trailer and properly operate the trailer lights. This harness will not do anything to help enable the Jeep to be towed.

For those that may chime in with a 2018 Wrangler, it would be helpful if you specified if your Jeep was the older JK model or the newer, JL model. In Jeep's infinite wisdom they built both models in 2018 and they are very different from a wiring/electronics perspective!