Pacbrake - Trailer Brake Issue

[kim2005]

Just purchased a 2005 Fleetwood Excursion with Cat C7. The first time I used the coach I was pulling a heavy 3-axle trailer going down a steep grade. I switched on the Pacbrake, and when I looked back, my trailer brakes were smoking. I had to reach down and turn off the trailer brakes, which wasn't a really good thing to do. I believe that the trailer brake is wired in somewhere near the brake pedal. I know when the Pacbrake is turned on the brake lights also come on. How do I keep the Pacbrake from activating the trailer brakes?

[wolfe10]

Welcome to the FMCA Forum.

There are quite a number of ways your trailer brakes could be activated including both surge and electric control from the coach. With that heavy a trailer (please verify that it is within the capacity of your coach-- if you need details on this, please ask) it should probably be set up on a separate brake controller. You sure don't want it to be on every time you use the exhaust brake.

[kim2005]

It is an aftermarket electric brake controller mounted under the dash just like you might find in a pickup truck. I'm not sure where this is wired in but normally they attach right after the brake switch on the pedal. So when the pacbrake is activated it activates the brake lights which sends power to the aftermarket brake controller, there must be a solution to this.

[pscarey1]

I have the same issue in my coach. I usually turn off the brake controller when using the pac brake downhill. I have a Tekonsha Prodigy controller. From what I can gather the brake controller is activated by the brake light circuit. Once activated it works like a surge brake using momentum to vary the amount of braking applied to the trailer brakes abd based upon the amount of bias you have set. Unfortunalely I have found no solution to the issue of burning up the trailer brakes while going downhill with the pac brake on.

[absolutelyranita]

You may also wish to contact Pacbrake by calling them in Blaine, Washington at 604-882-2382 or by emailing: leigh@pacbrake.com

[Koliver]

Sounds like they are set to come on proportionally with your brakes on the MH, whether by depressing the pedal or activating the Pacbrake. Sounds like they need to be adjusted. Sorry, I don't know how the adjustment works, but I think your trailer should always brake when the MH brakes, so rather than turning the controller off, you need to adjust it to provide the correct amount of braking.

I have a Pacbrake that keeps the brakelights on when it is activated, and that also keeps the trailer brakes on. Mine works just as it should, so yours should too.

If you find how to adjust, please post the solution.

[chucknewman]

Posted by Koliver,

"...I think your trailer should always brake when the MH brakes..." is absolutely correct. The key here is when the Pacbrake is operational, the MH brakes are not being used. At least in most applications.

The problem stems from the fact the trailer brake controller "wakes up" when it sees +12vdc from the MH's foot brake switch. As it does in any vehicle. The issue being when the Pacbrake is being used (as going down a hill) the ECM activates it with a voltage command to the "Pacbrake relay" as it normally would, but is also activating another relay that puts +12vdc on the brake light circuit. Unfortunately, this voltage is now placed onto the "brake switch" line to the trailer brake controller. It wakes up and is trying to do it's job when it really isn't needed.

I did a quick search of Pacbrake documentation. Didn't find a simple solution. Please let us know if Pacbrake has a solution.

The basic problem is the trailer brake controller does not know where the brake switch voltage is coming from. It just knows to proportionally apply the trailer brakes when the brake switch line goes hot. It assumes you are pressing in the brake pedal.

As Koliver also posted "I have a Pacbrake that keeps the brakelights on when it is activated, and that also keeps the trailer brakes on. Mine works just as it should, so yours should too."

It may simply be one or more adjustments to the brake controller need to be made.

More exotic fixes for this exist, but it does not appear to be a widespread problem (from lack of posts) and indicates a simple solution. Check with the brake controller manufacturer as well as Pacbrake.

Chuck

[wolfe10]

Good advice-- indeed contact the brake controller manufacturer and either PacBrake or more likely, your coach chassis manufacturer (since the chassis maker installed and did the wiring for the PacBrake, foot brake and brake light wiring).

Ideally, you want the trailer brake controller activated ONLY when the service brake/brake pedal is used, NOT when just the exhaust brake is on.

Brett

[kim2005]

Thanks for the suggestions. When I contacted pacbrake technical department I was a bit concerned when he told me he was unaware that the brake lights were activated when the pacbrake was turned on. They are going to do more research and get back to me. One of the easiest solutions might be to disconnect the relay that activates the brake lights when the pacbrake is turned on, but I dont know where to find that relay.

[kim2005]

To respond to Koliver, That might work fine going down a short hill or if your trailer brakes are worn or out of adjustment but if you are going down a long grade and using the pacbrake then the trailer brakes will be on the entire time and burn them up.

[wolfe10]

Yes, it is the chassis/coach maker's decision on whether the exhaust brake activates the brake lights, so PacBrake would not necessarily know.

[desertdeals69]

On most applications, the brake lights come on when the exhaust brake is energized. The reasoning is that it is the same as if you applied the brakes. I have worked with the manufacturer of wiring harnesses that supply Spartan and Freightliner. Most likely the trailer brake control needs to be activated only when the brake pedal is pushed. May require a separate switch.