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kb2ztx · 03-20-2016, 11:23 AM

So after a lot of reading I selected the factory mopar harness for our JK. I installed the harness a few months ago. This week we got our brake buddy in so today decided to test the new tow bar and all the other new parts. We have never towed the JK so this was all new stuff. So after reading instructions with brake buddy it says to test 5 times. When I do this the brake lights come on which I'm good with. What I'm not happy with is if the signals are on in the motor home it stops on the JK when the brakes get pushed.

Being I'm not really sure how much the brake buddy goes on (Towed the jeep 10 miles and seemed fine) do I need to worry about a brake wire switch or not ? I thought the mopar harness eliminated the need for this but guess not.

Does anyone else have this setup ?

**Lt Dan** · 03-20-2016, 12:49 PM

Okay, so I learn something new every day on this Forum. I have had my Mopar harness for over a year and never noticed what you are talking about. I just hooked up to check it and sure enough I see the same thing you brought up. With the turn signal on, the Jeep brake light overrides the turn signal. I did notice that there is a slight variation in the brightness as the turn signal cycles. Like you, now I have to decide if I want to install some kind of switch or relay to kill the Jeep brake lights. The monitor on my RVI2 brake system lets me see when it is braking, so I guess if I'm aware that this happens I can just make sure to "pump" the brakes so I don't get a continuous outage of the turn signal. Another possibility would be to pull the brake light fuse when towing, but that could be a PITA!

It makes sense though, since the Mopar harness uses small relays to activate the turn/brake signals from the motor home. When the relay cycles off for a turn signal, it's still getting power from the Jeep brake lights. Others with the extra bulb installed in the tail assembly have reported the same thing, both operating at once.

l1v3fr33ord1 · 03-20-2016, 02:07 PM

Roadmaster sells a relay to modify this behavior. Here's a link to the product page on etrailer.

Since this behavior is not limited to vehicles equipped with the Mopar harness, recent threads with alternatives to the Roadmaster relay are applicable. There have been several in the past two months. I'm sorry I can't find them for you right now. "FIRE UP" has written some posts on the topic, so you can search for posts by his user name.

**Lt Dan** · 03-20-2016, 02:43 PM

After some thought, it should be fairly easy to hook up a relay cutout for the brake lights. A switch could accidently be left turned off and you would have no brake lights on the Jeep. Here is a simple solution with two diodes and a normally closed relay. When either turn signal is operating, the Jeep's brake light would be disabled with each flash. When the motorhome's steady brake light is activated, then the relay would be activated continuously. Either way, the turn signal should flash normally on the Jeep. The only thing you would lose is the third brake light, which would no longer activate when the Jeep's brake pedal is depressed.

This system would also work on toads with the second bulb installed in the taillight assembly.

kb2ztx · 03-20-2016, 03:14 PM

The crazy part is the mopar harness needs a power wire. I had to run this from my battery as the lights wouldn't work without them. I guess I assumed the relays would open the circuit to the brake lights. Being I am running a power lead to the JK to keep the battery topped off I think I'll add a relay to open the circuit when the harness is plugged in. That way I don't forget when I get somewhere to put a fuse in or flip a switch.

In reality I think the brake buddy only brakes on a hard stop from what I can read. During my test I don't think it braked at all but not sure how I would know. Maybe its not really an issue I need to worry about.