Air Compressor Riddle

[Nellie Wilson]

This is related to my 'Intermittent Air' post, but kinda different too.

I'm about to bite the bullet and swap out the unloader valve. Probably the (nearly new) governor too, if I can do so without breaking the d*** lines. My pals in White River Junction so jury-rigged everything, I should probably get new lines made up and start from scratch. I'd love to get one of those remote governors and mount it over my bed... then I could change it every morning, just to be safe. 

But, per usual, the 'I wannas' take a back seat to the 'I haftas.'

The bus has operated flawlessly since the 'no air' incident... airs up reasonably fast, unloads and re-loads when it should (Jack adjusted the governor) and holds air after shutdown. Of course, this flawless operation has all been while sitting safely in Jack's yard. But two miles down the road...?

(I do hear a new leak somewhere, but it seems unrelated – I'm guessing it sprouted when being over-pressurized).

So, my riddle: What (mechanically) changed by adding shop air? I mean, if the compressor would not load, why would it start working again after airing it up?

Yeah, I'm going to swap the parts but I'd still like to identify the problem. Trouble is, I don't know what I'm looking for.

Thanks Again,

Nellie Wilson

[JackConrad]

Nellie,
   I think BK said the compressor started working on the way to our place, not as soon as shop air was used to fill the tank.  I think something was stuck and then unstuck while BK was driving the coach to our place. As to what stuck and unstuck ??   Jack

[PCC]

The thingamijig that stops the air from going back outside after going through the compressor probably decided that if you were going to force the issue, the pressure from the added air would be allowed to move that thingamijig into the closed position, giving you system pressure; now it chooses to move freely and properly.

So a sticky thingamijig is probably the cause of this journey into the 'havetados', and I think that replacing it will prevent a repeat problem from happening.

Always remember, replacing means that it probably never would have failed again, but keeping it means it probably would have happened again at the next inopportune time.

[ruthi]

PCC, boy that is soooo right. It always happens that way, so, we figure may as well fix it anyways.

[gumpy]

Before you to the replacement work, you might want to figure out what that new leak is. A significant leak or possibly failure of a shuttle valve could cause the symptoms you described and prevent the system from airing up. Adding shop air could add enough extra pressure to seal the leak up enough to allow it to continue airing up. I know. It's a long shot, but I had similar issues when one of my airbags developed a significant leak. I could not hear the leak but it was enough to not allow the system to air up.