Brake Release

[737Captain]

Apologies upfront, this may be a long post.

I recently purchased a 2018 Phaeton 40IH, my first motorhome. The first time I drove it I noticed the brake pedal didn’t have much, if any free movement and felt like a bit of an on/off switch, no “feel”. I figured this must be normal, this is my first experience of air brakes and I’d had a professional pre buy inspection which mentioned nothing on the subject.

I had my F150 Powerboost truck fitted with Blue Ox baseplate and a Demco AF 1 brake system installed and used the reed switch connected to the optional wireless transmitter allowing me to have the brake indicator on the dashboard rather than the standard rear view mirror mount. I noticed that sometimes, maybe 30% of the time the brake indicator lights remain on after I released the brakes. A quick tap of the brakes fixes it. There is no consistency to it, it doesn’t seem to matter if I release the brakes suddenly or slowly, if they have been set a long time at a traffic light or just used momentarily to slow, completely random.

My first thought was the reed switch was sticking, I spoke to Demco and they suggested either the cable tension was set incorrectly or maybe the tail of the cable was getting hung up.

I then got to think that maybe the brakes really weren’t releasing fully, honestly I didn’t see or feel any difference in pick up performance from a stop

So I’m thinking probable causes are:-

AF1 brake cable set incorrectly
Coach brakes not releasing fully sometimes
AF1 controller problem

I’d appreciate you thoughts on the best way to approach this issue or ideas of other things it may be.

Thanks in advance.

[SafariBen]

I'm not familiar with the brake controller, where does the reed switch attach to the air brake system? the pedal or air pressure? That seems like the most likely cause of the 30% of the time it doesn't shut off.



The treadle valve feeling "on/off" without modulation is common at the very light application end. They often don't do light braking very well. There should be good modulation at the middle and hard brake force levels though. The treadle valve is easy enough to find and cheap to replace, but not the only possibility. Here's some diagnostics for the treadle valve:

https://www.youtube.com/watch?v=PniwT4xDsFU

[weighit]

I have the wireless monitor also on my motorhome dash and saw the light stay on after releasing the foot brake pedal. Sometimes if I brake harder, the light goes on and then off right away when brake pedal released. Other times not, so got on my knees and looked at the cable routing to the car brake pedal. Saw it was run through the factory carpet and they made a small hole for that cable. But it was slightly off center making the cable drag. So made the hole in the carpet a bit larger, and that fixed the light on the dash issue. I think that with the drag it did keep the brakes on the car on longer than needed.

[737Captain]

Originally Posted by weighit

I have the wireless monitor also on my motorhome dash and saw the light stay on after releasing the foot brake pedal. Sometimes if I brake harder, the light goes on and then off right away when brake pedal released. Other times not, so got on my knees and looked at the cable routing to the car brake pedal. Saw it was run through the factory carpet and they made a small hole for that cable. But it was slightly off center making the cable drag. So made the hole in the carpet a bit larger, and that fixed the light on the dash issue. I think that with the drag it did keep the brakes on the car on longer than needed.

Thank you, I’ll certainly check that out

[737Captain]

Originally Posted by SafariBen

I'm not familiar with the brake controller, where does the reed switch attach to the air brake system? the pedal or air pressure? That seems like the most likely cause of the 30% of the time it doesn't shut off.



The treadle valve feeling "on/off" without modulation is common at the very light application end. They often don't do light braking very well. There should be good modulation at the middle and hard brake force levels though. The treadle valve is easy enough to find and cheap to replace, but not the only possibility. Here's some diagnostics for the treadle valve:

Thanks so much, the reed valve attaches to the piston that actuates the brake pedal in the truck.

The brake troubleshooting YouTube is perfect, again thank you I’ll follow up.

[Argosy]

You had a problem before the AF1 was installed, I'd concentrate on that. Have you looked at the brake pedal to see of it's free? Sand, dirt, crud can corrode and bind. The O rings in the treadle valve can be hard and dry and binding instead of moving freely.

[FLYAway1]

Is your coach showing both fully charged air systems when you are checking the TOAD brakes? Remember, it takes air to release the brakes. If you have an actuator, fitting or line that fails, the brakes will apply. As the AF1 is an air proportional system from the coach system, without proper coach air you could have TOAD brake issues. If you have an air leak between the coach system and the TOAD system, the TOAD air cylinder will actuate the TOAD brakes. Also, checking the TOAD brake actuating cable run as advised is probably the first place that I would start trouble shooting.
Happy Trails and enjoy that FLUF you fly!
Ron, Marsha, Piper and now Daisy.

[737Captain]

Originally Posted by FLYAway1

Is your coach showing both fully charged air systems when you are checking the TOAD brakes? Remember, it takes air to release the brakes. If you have an actuator, fitting or line that fails, the brakes will apply. As the AF1 is an air proportional system from the coach system, without proper coach air you could have TOAD brake issues. If you have an air leak between the coach system and the TOAD system, the TOAD air cylinder will actuate the TOAD brakes. Also, checking the TOAD brake actuating cable run as advised is probably the first place that I would start trouble shooting.
Happy Trails and enjoy that FLUF you fly!
Ron, Marsha, Piper and now Daisy.

Thanks Ron,
The more I get into it the more I think about it the more I believe it to be cable adjustment at the truck pedal. Hoping to get to the bottom of it today.

[twinboat]

Originally Posted by FLYAway1

Is your coach showing both fully charged air systems when you are checking the TOAD brakes? Remember, it takes air to release the brakes. If you have an actuator, fitting or line that fails, the brakes will apply. As the AF1 is an air proportional system from the coach system, without proper coach air you could have TOAD brake issues. If you have an air leak between the coach system and the TOAD system, the TOAD air cylinder will actuate the TOAD brakes. Also, checking the TOAD brake actuating cable run as advised is probably the first place that I would start trouble shooting.
Happy Trails and enjoy that FLUF you fly!
Ron, Marsha, Piper and now Daisy.

Flyaway, if your under the assumption that the service brakes work by releasing air, you are WRONG.

It's true that the PARKING brake is held released by constant air but not the service or normal stopping brakes. They are applied by air pressure from the tanks, thru the foot valve, when you step on it. They are 2 independent systems.

[jandcr]

Originally Posted by twinboat

Flyaway, if your under the assumption that the service brakes work by releasing air, you are WRONG.

It's true that the PARKING brake is held released by constant air but not the service or normal stopping brakes. They are applied by air pressure from the tanks, thru the foot valve, when you step on it. They are 2 independent systems.

Good point. That is fail safe for the parking brakes. If you watch Highway Through Hell, or the other heavy rescue programs, note that they need air pressure to release the brakes when towing a tractor or trailer. Otherwise, they have to crawl underneath and "cage" the brakes manually on each wheel. It would be the same for the motorhome unless they could run an air feed from the tow truck. Hmmm... maybe that's what the air chuck is really for in the front basement.

[FLYAway1]

Twin boat , with all due respect, I believe that I am correct.
At idle with both air tanks fully charged, pressure in the lines release the brakes. When you step on the brake pedal (treadle valve) you decrease air in the lines which allow the actuators to apply the brakes. If you have no air in the lines of the normal braking system, you cannot release the brakes. That is why you “cage” the brake actuators to tow or need to hook up an air line to charge the brake lines.
The parking brakes work the same only just on the rear axel and they have a positive on/off valve.
It ALWAYS Takes air to release the brakes and releasing the air to apply the brakes.
Happy Trails!
Ron, Marsha, Piper and now including Daisy

[bentjm]

Originally Posted by FLYAway1

Twin boat , with all due respect, I believe that I am correct.
At idle with both air tanks fully charged, pressure in the lines release the brakes. When you step on the brake pedal (treadle valve) you decrease air in the lines which allow the actuators to apply the brakes. If you have no air in the lines of the normal braking system, you cannot release the brakes. That is why you “cage” the brake actuators to tow or need to hook up an air line to charge the brake lines.
The parking brakes work the same only just on the rear axel and they have a positive on/off valve.
It ALWAYS Takes air to release the brakes and releasing the air to apply the brakes.
Happy Trails!
Ron, Marsha, Piper and now including Daisy

twinboat is correct.

The service brakes are actuated by air pressure.

The parking/emergency brakes are actuated by springs and are held open by air pressure.

[twinboat]

Originally Posted by FLYAway1

Twin boat , with all due respect, I believe that I am correct.
At idle with both air tanks fully charged, pressure in the lines release the brakes. When you step on the brake pedal (treadle valve) you decrease air in the lines which allow the actuators to apply the brakes. If you have no air in the lines of the normal braking system, you cannot release the brakes. That is why you “cage” the brake actuators to tow or need to hook up an air line to charge the brake lines.
The parking brakes work the same only just on the rear axel and they have a positive on/off valve.
It ALWAYS Takes air to release the brakes and releasing the air to apply the brakes.
Happy Trails!
Ron, Marsha, Piper and now including Daisy

I have training certificates in air brakes, I'm not wrong.

You cage the spring brakes, but not the service brakes. The rear brake chambers are dual chamber, 1 for parking, with the large spting and the other for the service brakes.

[FLYAway1]

Doing research, you are correct regarding the Freightliner chassis. I was taught years ago the other way of airbrake operation for commercial vehicles. I am not sure if all commercial vehicles are this way now or just Freightliner. The steam locomotive that I drove years ago worked the same way with its Westinghouse air compressor. No air, no go. I wonder if there is a safety advantage or just more cost effective.
Sorry for any confusion.
Happy Trails!
Ron, Marsha, Piper and now Daisy