Audible alert from Allison panel

[Mr. Jeff]

On our past several trips, after the first mile or so, we began getting a soft audible tone (a soft tone like a digital bell) . I can tell it's coming from the Allison panel. No visual dash alarms. Allison fluid level reports OK. No adverse characteristics or conditions. Audible stops when placing in Neutral. I'm at a loss - ideas what this is?

[Skip426]

What chassis is your coach on ?

[Domo]

Must be a Tiffin, perhaps on a Freightliner chassis, since this is also posted on the Tiffin forum site.

[Dutch Star Don]

I don't know what chassis the older Allegro Bus uses, but Freightliner uses a soft bell sound for issues. It should be showing something on the dash. I've never heard of Allison using any type of sound indicators for issues.

[Skip426]

2000 Tiffin ; if built on Freightliner chassis , most likely a bad sensor for the park brake not released warning ( since it quits in neutral).

That vintage of Freightliner chassis had redundant sensors for park brake release ; one for the buzzer , one for the light.
Buzzer on and no light , one sensor is bad .
Light on and no buzzer , the other sensor is bad .
Both buzzer and light on,= low air pressure at the park brake release chamber.

Mr.Jeff ; if you'll confirm your chassis , I'll post pictures of the sensor and where to find it.

[Mr. Jeff]

Thanks for the replies, sorry for not noting frame and model - 2000 Allegro Bus, Freightliner chassis, Cummins engine

[wolfe10]

If the code is coming from the Allison transmission, use the shift pad (engine off, key on) to check for DIAGNOSTIC CODES.

[Skip426]

Originally Posted by Mr. Jeff

Thanks for the replies, sorry for not noting frame and model - 2000 Allegro Bus, Freightliner chassis, Cummins engine

Ok ; for a test , when the noise is present idling in gear set the park brake , if the noise gets a little louder or stays the same ; release the park brake quickly . Even do it a couple of times ; if the noise quits momentarily on the release of the park brake .
The pressure sensor is faulty .
Inside the drivers side frame rail above the LR wheel brake chamber there is the manifold pictured below attached to a black plastic tube to the park brake release chamber . There are two sensors , two wire sensor is for the park brake on light ; the three wire sensor is for the park brake on in gear buzzer.

Highlighted in this air system diagram. (pdf)

[Mr. Jeff]

Skip - Thanks for the information!! Awesome info. I'll crawl up under there in the cool of the morning.

[Skip426]

Originally Posted by Mr. Jeff

Skip - Thanks for the information!! Awesome info. I'll crawl up under there in the cool of the morning.

Remember to have solid blocking to the frame ; do not rely on levelers .

[Mr. Jeff]

Indeed!