Engine brake and trailer brakes

[twp5253]

I have followed this and other threads and I must admit I am not sure what is happening with my trailer brakes when using the Jake Brakes. I think I looked down at the P2 Brake Controller and did not see it applying voltage but I was pretty overwhelmed with some steep hills and I sure know how to toggle from hi to low on my Jake

For the OP, I would ask you answer your own question. Do this simply by looking at the P2 brake controller. It will show you what is going on. If it is applying brakes and you don't want that to happen, you can dial down the sensitivity of the device. I had installed a P3 on my Ridgeline to bring my 26' total length trailer down to the RV dealer. It operates almost the same and I was able to dial in the right settings so I got the braking that I wanted. I have not found that to be as easy on the XL because frankly, I don't think I need the trailer brakes on that beast! I have the settings pretty low on the P2 controller in my M2.

[Webefine]

This has been discussed quite a bit on here so some searches in the Dynamax thread should get you your answers. It seems that the latter years of the M2 chassis do bring on the brake lights when the engine brake engages, so if your trailer brake controller uses your brake lights as a signal then your trailer brakes are most likely coming on. There is a fix for this that involves installing a pressure switch in the air line that is activated by applying the brake pedal. My 2015 DX3 does not bring on the brake lights with the engine brake so I did not need to do the pressure switch setup. I hope this points you in the right direction.

[CyberShanks]

I can confirm our 2021 XL also lights up brake lights when the engine brake activates.

I have a prodigy p3 in it and ever so slightly do the trailer brakes engage due to it being a proportional brake controller. If I get on the brake pedal manually, then the trailer brakes activate at the same braking momentum I'm applying to the truck.


Jim

[KRedburn]

Yes, the brake lights on a M2 chassis do come on when engine brake is activated. This is a DOT requirement for a commercial chassis which the Dynamax is based on.
Yes it can be programmed out if you chose to spend around 300 bucks.

Do note that the trailer braking with the Prodigy unit was for a time improperly implemented in the PAST. I can only speak regarding the 2018 DX3 that I own. The Prodigy unit was using the brake lights signal for activation of the proportional braking to a trailer.

Newer models of the Dynamax (I believe by 2020 and newer)changed the implementation of the Prodigy unit by putting a pressure sensing switch in the green air line near the firewall driver side. If you have this pressure switch then your trailer braking will only be activated by you applying vehicle braking using the brake pedal. Engine braking will only control braking of the M2 MH.

There are other implementations of making this happen that have been described in other threads regarding engine braking and trailer brakes.

Also note: a pickup implementation is completely different regarding trailer braking since the M2 is an air brake system and the brake pedal switch is a grounding switch as opposed to switching 12vdc. Therefore, trying to compare a pickup to a commercial truck chassis has no bearing.

[dalford]

Back to op. The engine brake does not apply mechanical wheel brakes.

It has been shown in this thread that the eb turns on brake lights on some rvs but it does not apply the mh brakes.

Anyway, don’t want to sound like an internet expert but everything but what is asked is answered.

[Mike134]

Originally Posted by dalford

Back to op. The engine brake does not apply mechanical wheel brakes. But it does apply the trailer brakes when they are towed behind SOME Freightliner Chassis Motorhomes. Which was the Op's question

It has been shown in this thread that the eb turns on brake lights on some rvs but it does not apply the mh brakes. Correct

Anyway, don’t want to sound like an internet expert but everything but what is asked is answered.

revised your comments based on what other Freightliner owners posted

[dalford]

Originally Posted by Mike134

revised your comments based on what other Freightliner owners posted

Mike, I stand corrected… I’ll stick to truck and trailer posts in the future..Thx

[TexasChris]

So unfortunately the trailer we drove 720 miles to get wasn't ready, so we came back home without it. We are possibly going back in two weeks to get it, I will do some test on the way home.

[dalford]

Originally Posted by TexasChris

So unfortunately the trailer we drove 720 miles to get wasn't ready, so we came back home without it. We are possibly going back in two weeks to get it, I will do some test on the way home.

Bummer it was not ready!

What kind of trailer is this? A large utility trailer to pull behind your MH?

[CyberShanks]

Truly sucks about your trailer not being ready. I'd think I would set up camp and wait till it was with today's fuel prices..


Jim

[twp5253]

Before driving 1200 miles to pick up my trailer in Middlebury, IN, just 5 miles from Elkhorn, I asked the dealer to send me pictures showing not only the trailer, but the options I had ordered and paid for.

This technique almost worked for my XL but I am not going to beat that dead horse at this time.

[Eric H.]

Originally Posted by doc73

Apparently everyone but yourself

The trailer brakes are not powered/energized by the brake light power. The brakes get there power from pin# 2 in your 7 pin connector dedicated to the trailer brakes. The brake light signal only goes to your controller so the controller knows when to apply the pin#2 power to the brakes.

[twp5253]

Originally Posted by Eric H.

The trailer brakes are not powered/energized by the brake light power. The brakes get there power from pin# 2 in your 7 pin connector dedicated to the trailer brakes. The brake light signal only goes to your controller so the controller knows when to apply the pin#2 power to the brakes.

It is always good to know the mechanics of something and I agree with your post. I think the point of this thread is something quite different. When the M2 owners are using their EB or Jake Brakes, there are several more variables at play. Some M2s turn on the brake lights and some don't. Then, if the brake lights get illuminated, the question at hand is whether that will be a signal the P2 controller sees to "wake up" and possibly start applying power to the trailer brakes. My limited experience in my 22 XL is that my P2 does not send any signal to the trailer brakes while I am slowing down via my Jake Brakes. I will spend a bit more time confirming this as that signal is visible on the LED panel of the P2 controller. It can also be "dialed down" with the adjustment wheel.

Hope this helps as I am still unsure of the answer to the OP's question.

[Eric H.]

Originally Posted by twp5253

It is always good to know the mechanics of something and I agree with your post. I think the point of this thread is something quite different. When the M2 owners are using their EB or Jake Brakes, there are several more variables at play. Some M2s turn on the brake lights and some don't. Then, if the brake lights get illuminated, the question at hand is whether that will be a signal the P2 controller sees to "wake up" and possibly start applying power to the trailer brakes. My limited experience in my 22 XL is that my P2 does not send any signal to the trailer brakes while I am slowing down via my Jake Brakes. I will spend a bit more time confirming this as that signal is visible on the LED panel of the P2 controller. It can also be "dialed down" with the adjustment wheel.

Hope this helps as I am still unsure of the answer to the OP's question.

I've read every post and know what the topic is about, how many people have misunderstood the question and which vehicles it applies to.

My reply was specifically to someone who did not understand another post about where the power comes from for the brakes.