AD-9 Air dryer questions

[TheHubbardBus]

LOL @ECCB


This is our governor. He's been around far too long here so age may be a factor in him not working. Has eye-ports far too close together. And he's expensive, though if you have enough money he's up for sale to the highest bidder.

[cadillackid]

Originally Posted by TheHubbardBus

Thanks Native. Unfortunately the only electric components in the system are heaters, & they shouldn't be part of the problem (to my knowledge).



The purging is controlled by air pressure via governor, which itself is controlled by air pressure from the reservoir and the compressor.

one thing i have found is that if the Bus has a really small wet tank.. (one of those 3-in-1 tanks. then the air pressure in the wet tank drops down very quickly during purge and triggers the governor right back on right after the purge.. since the wet tank is so small. the compressor doesnt run long and it kicks off again.. so you get purges every 30-40 seconds or so... my DEV bus has that 3 in 1 tank but there is also a much larger tank which appears to at one time to have been a wet tank. and it is bypassed.. im guessing it leaks so the school bypassed it... my superior has that larger wet tank and so the governor doesnt purge nearly as often...


-Christopher

[TheHubbardBus]

Thanks guys.

So at this time, I would like to say,

I'VE GOT EVERYTHING WORKING!!!!!!!

Dryer's purging as it should, system's holding pressure just fine, No leaks anywhere.. Life is muy bueno!!!

To everyone that's helped us along the way. This air brake fiasco has been crazy.

Turns out, from the time we picked up the bus (from Austin ISD), the governor had been configured wrong. Plug in the unloader port was preventing the governor from unloading, ever. I replaced the governor, but at the time, didn't understand how the air brake system worked, so I reconfigured the new one exactly like the old.

We never realized the compressor was never kicking off because of all the leaks - and I gotta think all the leaks may have been caused by the compressor never kicking off. Either way, a whole lot of fittings, a rebuilt dryer, and now a properly-installed governor later, we've got an air brake system that finally works!!!!!

Thank you to EVERYONE that helped us along the way. I'm actually happy it worked out this way in the long run, because I know more about the system than I ever would have learned 'the easy way'.

[Native]

That is wonderful news, congratulations!

[Booyah45828]

That's great news! Kudos to you for figuring it out, and you learned how the system operates in the process.

So with the compressor never kicking off, the air coming from the exhaust on the dryer was just air from the compressor then? I'm surprised somebody goofed on something like that at the district and didn't notice it.

Is your governor mounted on the compressor? Or is it mounted elsewhere?

[TheHubbardBus]

Originally Posted by Booyah45828

So with the compressor never kicking off, the air coming from the exhaust on the dryer was just air from the compressor then? I'm surprised somebody goofed on something like that at the district and didn't notice it.

Is your governor mounted on the compressor? Or is it mounted elsewhere?

Exactly. One thing I should have noticed early on was that the purging increased with RPM. But I'm usually working on it alone, and can't hear much over bus noise on the few short trips we made. And I don't know if I would have known enough about it early on to make the connection even if I had.

Yes. It's mounted on the compressor, so the control / unloader port (which was plugged on the compressor side) links to the compressor right at that gasketed interface. That was another point where my ignorance came into play. Now, a plug there would have stood out like a sore thumb as 'no go'. Then... I was just playing copycat.

Surprised... I'm wondering if maybe it wasn't done on purpose to offset all the leaks we had by keeping the compressor running non-stop. Just conjecture. Who knows. But it's reaffirmed my long-standing rule of never trusting anyone - myself included

[Booyah45828]

Originally Posted by TheHubbardBus

Yes. It's mounted on the compressor, so the control / unloader port (which was plugged on the compressor side) links to the compressor right at that gasketed interface. That was another point where my ignorance came into play. Now, a plug there would have stood out like a sore thumb as 'no go'. Then... I was just playing copycat.

That makes sense, and is perfectly acceptable as to why it was missed. I mean unless you know how it's supposed to operate, one could very easily overlook that. If it was remote mounted, then you'd have a hose running to it, which would be hard to miss/overlook.

I've seen sometimes those plugs pre-installed, so maybe that's the case here and whoever installed the governor originally didn't know.

Who knows though.

Glad it's fixed and you can move onto the next item.

[Superdave99709]

On the compressor top there is a batman symbol looking plate under this is poppets they are worn out change them.

[Superdave99709]

Originally Posted by TheHubbardBus

Thanks mmoore.

I don't think it's the check valve, as it was the 2nd thing I replaced after the governor trying to fix this issue.


I'm still learning all this stuff, but I'm starting to believe it might be the unloader mechanism of the compressor itself.

On top of the compressor is a batman symbol shaped plate. Under this plate are 4 poppets. These are worn out. Replace them. It's pretty easy to do.