[Archived]

Dean, different converters and different models of Prevost have different pneumatic systems on the accessory side. I have found that a whole lot of chasing air leaks is easier done if I know where every line goes.

The Prevost side of the accessory or aux system is easy because they have pneumatic diagrams.

On the converter side you may have to chase the individual circuits yourself, but I have begun a project that is going to be a huge help now and in the future. I am finding the distribution point for accessory air, both Prevost and converter side, creating a new manifold block that has a ball valve on every single line that goes to the components and that will do two things for me.

First, I can shut off every valve after I have aired up the entire coach. When I come back a little while later I open each valve and on every one that I hear air passing through it, I know I have a leak somewhere in that circuit.

The second advantage is I can isolate circuits, turn them off for servicing, while I don’t need them to minimize the compressor run time, or to just disable the feature.

I have been able to buy all my needed parts and fittings on Amazon and when I have gathered everything I will spend a few hours putting it all together. It is not rocket science and the benefits are well worth the effort. I have the converter side done now and my next project will be the Prevost side.

BTW, look at your seat as a likely source of leaks.

[Billy]

On the Marathon side the aux compressor supplies the generator airbags, the toilet if you still have a microphor, the awning windows if air operated, the pocket doors, the bed lift if you have one, the drop door in the water bay, and the sewer hose extension and retract, and I think the floor slide. I believe that is all. The pancake looking thing on the floor of the electrical bay under the driver’s seat is not a compressor, but is the accumulator tank for the compressor in the generator bay. It needs rto be drained regularly. There is another tank near the water bay and the drain for that is in the water bay on the curbside. It should be drained regularly also.

[Archived]

Dean,

Your dash gauge is for the Prevost aux air and can be at zero with no need to have any air until you start up. Before I start up, I crack the yellow valve to put air into the Prevost side to air up the engine bellows before starting. Ignore the zero unless it just drives you crazy and then you can start chasing air leaks in the rear.

Like cupcar explained, the Marathon side gets fed by the aux compressor in the generator bay and the only way to get air to the Prevost side is by opening the yellow valve.

[Archived]

Dean

You have a different setup with the Marathon then when you had a Liberty.

The Aux Air gage in your bus is supplied by the engine driven compressor in the back of the bus, Everything Cupcar listed is supplied by the electric powered compressor Marathon installed in your middle bay. The Marathon Aux tank is located in your front left bay. On the pancake tank you have a gauge that tells you how much air you have on the Marathon side. You said you don’t hear the house compressor come on much, that’s a good thing.

Your leaks are on the Prevost side, that’s why your seat and steering wheel column won’t work when you have no air on the Prevost Aux side, they are plumbed through there.

Later

bv

[Corey]

Thanks for responses. Everything you say makes since. The air pressure on the pancake tank holds steady which explains why the Aux compressor on the Marathon side doesn’t cycle too frequently. I am very happy about that. While at Marathon a few weeks ago they had to replace a valve on the drivers seat due to the seat adjustment not working properly. I have a hunch, as Jon said, that that is where my problem is. Having said that, it doesn’t sound like anything that I need to loose sleep over. I may have Jeff install a shut off valve to the seat that I can use when I shut the bus down. Thanks again for your help.

[Larry & Diane]

You should exersize that drain valve often on the bottom of the pancake tank but I doubt much will come out if the compressor doesn’t run often.

Just a note on what Tom is doing, after he loses his Prevost Aux air he doesn’t like to start his bus with the belt pulley air bags deflated so he is stealing air from the Marathon Aux tank by opening the yellow valve to get some air in the bags.

Later

bv

[John]

I am sure my seat leaks some, but the big leak on the Prevost side is in the engine compartment. Bellows, bags, tensioner, etc. Like truk my belts are slack in a day or two. Bernie, mine is an ’05 and the generator is in the front bay curbside. The tank is in the electrical cabinet under the seat. I know they moved them around, but, I mention this because the OP has a ’05 also.

Bob

[Peter]

Yes, I wrote Aux compressor was in the middle bay. It’s the front CS like you say.

Later

bv

[Archived]

I haven’t noticed the yellow valve that Tom referred to but I will look for it and do like he does before starting next time. Makes sense to me. I have drained the pancake tank a few times already and haven’t gotten any moisture out of it yet however you usually have to drain most of the pressure off before the moisture will come out.

[Peter]

It is nice to have a no leak coach and over the next year or so I am methodically going to replace valves and fittings to see if I can make that happen. But having done this dance on 2 previous coaches I know for sure as soon as i get it done I am going to restart the process of checking leaks.

What I did do on the previous coach however was to isolate the problem circuits that were not necessary when parked and shut the air off to them via a “key on” solenoid valve that I installed in their air circuit. In that manner if the problem circuit started losing air again it did not affect me when I did not need it. However, if a solenoid valve such as I installed fails to open air will not get to that circuit, and one that has always been an issue for most folks is the belt tensioner in the rear. You can do without air to the seat, but you cannot run the coach without air to the belt tensioners so on critical circuits if you install a solenoid valve, make sure you have a manual by-pass in the event ot a solenoid valve failure.