Mopar Tow Harness Install

[NavyVet1959]

Still haven’t been able to figure out the brake controller. There is an assumption that the brake pedal signal wire is not 12v causing it to not activate the trailer brakes when the brake pedal is pressed.

Is this with LED lights on the Jeep? If so, they might have figured that they didn't need to stick to the 12V standard. It's also possible that they just do not provide enough amperage even if it is 12V.

Do you have a multimeter? If so, measure the voltage...

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[mergedown]

Is this with LED lights on the Jeep? If so, they might have figured that they didn't need to stick to the 12V standard. It's also possible that they just do not provide enough amperage even if it is 12V.

Do you have a multimeter? If so, measure the voltage...

Yes, I have the LED package. It’s just crazy that they have it all set up for a brake controller in models with the tow package yet it doesn’t seem like we’ve found the right wire to power the brakes in models that didn’t come with the tow package.

I do have a multimeter and need to get a reading.

 

[NavyVet1959]

Yes, I have the LED package. It’s just crazy that they have it all set up for a brake controller in models with the tow package yet it doesn’t seem like we’ve found the right wire to power the brakes in models that didn’t come with the tow package.

I do have a multimeter and need to get a reading.

Single LEDs do not need 12V to produce light. In fact, if they are supplied with 12V, you might see a very small flash if you are looking very closely at it and then they will become a DED -- Dark Emitting Diode.

LEDs typically have a forward voltage of anywhere from 1.7V to 3.4V. This is the voltage drop that occurs across the device. It varies with the color of the LED. Is Jeep using red LEDs or are they using white LEDs and have a red filter over them? A typical high efficiency red LED will have a forward voltage of around 2V and a white high efficiency will have around 3.2V. If you want to run these with 12V, then you need to put a resistor in series with the LED and that resistor will need to drop the extra voltage. Of course, it needs the proper wattage rating since it is going to be dropping that voltage in the form of heat. The resistor is also there to limit the current since you only want about 20 mA through a single LED. Previously, LEDs were an aftermarket affair and all the LED suppliers made them work with existing 12V supplies by possibly putting multiple LEDs in series and/or putting appropriately sized current limiting resistors in the lamp's housing. A car manufacturer on the other hand might choose to supply a particular voltage that is advantageous for their particular LED assembly and that does not have to be 12V. There are indicator lights on the dash like for the ESS override. Are these LEDs? If so, did the manufacturer decide to supply exactly the voltage that the LED needed or did they decide to supply 12V and expect the indicator light to take the necessary steps to reduce it and limit the current? Not having received my JL yet, I can't make any measurements to try to reverse engineer their system.

Another thing to look at though is whether there is normal 12V wiring to the back of the Jeep even though you have the LED tail lights. Since you have to tell the vehicle's computer that you have the LED tail light option, I have to wonder if the engineers decided to only power one circuit or the other even if both circuits are run to the tail light connector.

It's a new system and there is going to be a bit of a learning curve as we discover what we can have to do to work around their design decisions.

 

[NavyVet1959]

Yes, I have the LED package. It’s just crazy that they have it all set up for a brake controller in models with the tow package yet it doesn’t seem like we’ve found the right wire to power the brakes in models that didn’t come with the tow package.

I do have a multimeter and need to get a reading.

Here's some of the thoughts that I have on how their system might be worked around.

https://sites.google.com/site/navyvet1959/vehicles/arduino-turn-signals

 

[mergedown]

Single LEDs do not need 12V to produce light. In fact, if they are supplied with 12V, you might see a very small flash if you are looking very closely at it and then they will become a DED -- Dark Emitting Diode.

LEDs typically have a forward voltage of anywhere from 1.7V to 3.4V. This is the voltage drop that occurs across the device. It varies with the color of the LED. Is Jeep using red LEDs or are they using white LEDs and have a red filter over them? A typical high efficiency red LED will have a forward voltage of around 2V and a white high efficiency will have around 3.2V. If you want to run these with 12V, then you need to put a resistor in series with the LED and that resistor will need to drop the extra voltage. Of course, it needs the proper wattage rating since it is going to be dropping that voltage in the form of heat. The resistor is also there to limit the current since you only want about 20 mA through a single LED. Previously, LEDs were an aftermarket affair and all the LED suppliers made them work with existing 12V supplies by possibly putting multiple LEDs in series and/or putting appropriately sized current limiting resistors in the lamp's housing. A car manufacturer on the other hand might choose to supply a particular voltage that is advantageous for their particular LED assembly and that does not have to be 12V. There are indicator lights on the dash like for the ESS override. Are these LEDs? If so, did the manufacturer decide to supply exactly the voltage that the LED needed or did they decide to supply 12V and expect the indicator light to take the necessary steps to reduce it and limit the current? Not having received my JL yet, I can't make any measurements to try to reverse engineer their system.

Another thing to look at though is whether there is normal 12V wiring to the back of the Jeep even though you have the LED tail lights. Since you have to tell the vehicle's computer that you have the LED tail light option, I have to wonder if the engineers decided to only power one circuit or the other even if both circuits are run to the tail light connector.

It's a new system and there is going to be a bit of a learning curve as we discover what we can have to do to work around their design decisions.

Zero reading from signal wire via a multimeter. Either I’m not tapping the wire properly, or it’s the wrong wire.

 

[mergedown]

Here's some of the thoughts that I have on how their system might be worked around.

https://sites.google.com/site/navyvet1959/miscellaneous/arduino-turn-signals

Oh boy, that seems troubling for my level of electrical experience.

 

[NavyVet1959]

Zero reading from signal wire via a multimeter. Either I’m not tapping the wire properly, or it’s the wrong wire.

You need to turn the turn signal on so that it is flashing. Then read each of the wires in relation to ground. If the vehicle's computer is controlling the voltage on the wire, then one of them should show some sort of voltage during the flashes. It might be a pretty low voltage though.

Now, having said that, there is another way that the engineers *could* have implemented it. Instead of the vehicle computer controlling the flashing, they could have gone with a more distributed design where they just send a command to the tail light that tells it to start flashing and then send another command to it to stop flashing. I've done similar designs over the years, but for considerably more complex systems. I think it is entirely overkill to do this on a turn signal, but you never know -- one of those damn kiddie engineers might have thought that it was "a neat feature" and decided to implement it. Beware of young engineers touting "neat features".

And, if they are just sending the commands like that, you're probably not going to catch it on your multimeter. The signal will be very short and probably very low voltage. You might be able to catch it on an o'scope or signal analyzer if you know what to look for.

 

[NavyVet1959]

Oh boy, that seems troubling for my level of electrical experience.

Well, just like relays are one level up from directly switched wiring, that would be the next step up from relays. It's overkill for the simple concept of being able to do trailer wiring, but if a manufacturer decided to completely change how things work on us, we have to be able to work around it.

I haven't completed my writings on the topic on that page, so it might be a bit more difficult to explain that need be.

You might want to try reading my thoughts on bypassing the ESS (Electronic Start Start) system on the Jeeps. I added a diagram to it that might make it easier to understand. The brake and turn signal issue is just another step up from that.

https://sites.google.com/site/navyvet1959/vehicles/wrangler-jl-electronic-start-stop

 

[cashby9000]

I did this install over the weekend.
This video helps.
I had minor issues. Getting through the firewall is the worst. Go through the interior instead of what the video suggests.
Use duct tape in the wire hanger and some lubricant.

 

[mergedown]

Well, just like relays are one level up from directly switched wiring, that would be the next step up from relays. It's overkill for the simple concept of being able to do trailer wiring, but if a manufacturer decided to completely change how things work on us, we have to be able to work around it.

I haven't completed my writings on the topic on that page, so it might be a bit more difficult to explain that need be.

You might want to try reading my thoughts on bypassing the ESS (Electronic Start Start) system on the Jeeps. I added a diagram to it that might make it easier to understand. The brake and turn signal issue is just another step up from that.

https://sites.google.com/site/navyvet1959/miscellaneous/wrangler-jl-electronic-start-stop

Fortunately, the harness itself is working fine. And manual operation of the trailer brakes via the brake controller are working fine. I just can’t seem to find a way to trigger the trailer brakes via the brake pedal signal wire.

 

[NavyVet1959]

Fortunately, the harness itself is working fine. And manual operation of the trailer brakes via the brake controller are working fine. I just can’t seem to find a way to trigger the trailer brakes via the brake pedal signal wire.

Was it previously working on another vehicle?

 

[mergedown]

Was it previously working on another vehicle?

It's brand new and never used on another vehicle. Considering I'm not getting a voltage reading from the pedal signal wire from the JL, I'd imagine that's the first thing to solve. If when I get a signal it still doesn't work, I guess we could then ask if the controller is faulty or the signal being sent isn't compatible?

 

[forrest]

This video helps.
I had minor issues. Getting through the firewall is the worst. Go through the interior instead of what the video suggests.
Use duct tape in the wire hanger and some lubricant.

I was thinking of doing that - poke through from the inside, tape the wire to it, then pull it back through.

There isn’t an existing hole, right? You just need to poke a new one anywhere in the grommet?

 

[Dubeau9005]

I was thinking of doing that - poke through from the inside, tape the wire to it, then pull it back through.

There isn’t an existing hole, right? You just need to poke a new one anywhere in the grommet?

I did the same thing. Poke hole from the inside. For ease of access, try to poke the hole on the right bottom corner of it when looking at it from in the Jeep. Makes it the easiest spot to grab the wire when you push it through.and no existing hole. Just use the large grommet. It is really soft and flexible. Stretches quite a bit to allow thicker section of wires through. Lubing the wires up definitely helps.

 

[RussJeep1]

No worries at all, just be careful as your pulling off the plastic trim. They come off pretty easy, but you don’t want to break any of the mounting points. Other than that it really wasn’t too bad, just time consuming.

Most difficult part was feeding the wire through the firewall.

Hey @mergedown Jason:

First off, I want to thank for documenting all your efforts here. It's people like you, and YouTube videos that cover stuff like this that are the real trail blazers to make the installs of us followers easier.

Second, I want to say I've read through the entire thread making sure what I'm about to say wasn't covered. I thought I owed you that. If I'm wrong, and missed it: apologies.

Third, my interest in this project lies only with how wires are snaked from the engine compartment into the cabin. I neither have, nor have need for a 7 pin trailer harness. I installed my own 4 pin from etrailer. with a battery wire running under the rig with zip ties and that's fine for me: no need for brake controller circuitry at my end; not at least at this time.

All these caveats said, and I assure you I do NOT want to sound like a wise ass, having learned first from you (and maybe that's key here) I decided to take a wire hanger, enter the rig from the front passenger's seat, and shove it through that grommet, which is below the glove box, with no need to remove the glove box (not that that step is hard).

After pushing an inch or two on the hanger wire I got on my back outside the rig and behind the front passenger's tire. I pulled back the fender flare a bit, by no means disturbing the hardware that keeps it in place, looked up with a flashlight and saw the tip of my hanger.

I put a pair of plyers on it and pulled it further. Though I'm no mechanic, but dropping wires down connected to the battery or PDC, to the pavement below, will be straight forward, as will be taping those wires on to the hanger, and pulling the wires through to the inside of the cabin at the grommet.

I can't help but think that all the work with the fender flare and glove box is questionable, but it may be my ignorance that has no me not appreciating why the install calls for these steps. And it's definitely true that I had the beginner's luck of deciding to push the hanger out from the interior, rather than vice versa: which I think would have definitely required me to cut the hardware that keeps the fender flare in place.

Thoughts?

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