[Archived]

If the toilet needs 60 psi like mine, you need to maintain pressures in excess of that number in your aux system, it’s all about volume. Mine uses 8 psi for a single flush, that’s why mine is set to 70/100. I’m sure you have an air regulator for the toilet, if not, forget everything I just said. Is yours a Microphor?

[Brian]

The bus air systems, particularly the aux suspension systems seem to be misunderstood. There are articles on this site that will help with the understanding of the system. The reason for stating 120-125 PSI system pressure for leveling is because some coaches, CC and Marathon are two that come to mind, tend to be heavy on the front so it may take all of that to raise the front. On the other hand only 70 PSI may be required to raise the rear. The pressures are all dependent on how much weight is on the axle. You have weighed your coach while fully loaded so you know your axle weights, right?

My comment about leveling is not to suggest you use the compressor for that purpose. In a perfect world your bus should not lean at all. If it leans after three or more days I believe that is the acceptable standard according to Prevost. If you have a coach in which the system logic requires aux system pressure above 35 PSI (approximately) to retain tag axle air bag pressure your leans may not be the cause of a leak in the air bags or valves associated with the leveling system, but may be due to loss of air pressure in the aux system dumping tag axle air bag air.

If you are confused you are not alone. As I have suggested on another thread it is always better to cure the underlying cause of problems such as aux system air leaks rather than adding a band aid fix such as relying on an aux compressor for leveling.

The reason I pulled your chain on axle weights is not to help you understand you may have to run high pressures to raise the front of your coach but because you do not know how much pressure to put in your tires unless you know the weight they carry which is another whole topic.

[Archived]

thers is a lot more to this than i was thinking i have not weighed the bus yet i will load and weigh in a week or so . I am pretty familar with the Microphor toilet as i am one of thier repair centers or was probly still am neaver did much but have a full understanding of the elect one , now i have an air one go figure . It rained here most all day so i was unable to get much done ill start picking on it in the am hurricane permitting again go figure , some times you cant buy a break. Thank again David

[Don]

I think the hardest thing for folks to do is to not look at the coach pneumatic system as a big complex system, but to mentally think of it as a number of individual relatively simple systems which function independent of one another but which share an air supply.

On the converter side of the coach that is fairly simple because nobody looks at the converter’s pneumatic system and thinks of it as a whole, but of individual devices that share a common air supply. The same is true of the Prevost pneumatic system which has a primary brake system, secondary brake system and an aux system. The aux system is comprised of a front suspension system, a left rear suspension system and a right rear suspension system. Additionally the aux system has a door lock, belt tensioners, etc.

Once a person breaks the pneumatic system down into its individual sub systems developing an understanding starts to come easy.

[Archived]

While on the subject of air needed to flush various toliets, While I was at Prevost getting work done Tuesday I was talking to a driver of one of the enertainer buses, I asked how often did he have to dump, concidering he was hauling around six to eight band members to gigs. His answer was short he said that he put a 90 degree fitting on the bus and just pulls over to the shoulder on the side of the road and dumps there! very seldom dumps ina sewer unless in service. I ask if he wasn’t afraid he would get caught, said he was not worried about it When and if he gets caught they will probably burn him a new one! Gary

[Archived]

Jon,

In what way does the Aux Air system interact with the suspension when the bus is running/driving? Does the Aux compressor need to be powered on when driving? I have a 2000 (1999 Chassis) XL Country Coach.

Chris

[Archived]

Good question Chris and I’ll try to go a little beyond with the answer.

We do not need aux compressors for our coaches at all. I’ll qualify that in a moment. Our pneumatic systems are supplied sufficient air pressure and volume by the engine driven compressor. The primary use of air is for the braking systems and with the exception of some coaches, auxiliary air will not back feed into those systems so an auxiliary air compressor serves no real purpose, even as back up as long as the engine is running and the compressor is working.

Our suspensions require air and that supply is auxiliary air meaning it is the air pressure available from the engine driven air compressor for the auxiliary bus air system once the brake systems are satisfied.

In almost every case when air is needed for the suspension the bus is running and the compressor on the engine is supplying the needed air. That air keeps the bus level with respect to the ground while we are driving, and when we are in a campsite and want to level the coach (with respect to the horizon) we also have the engine running. When we turn off the engine, we are also “locking” air in the suspension system so the bus stays level.

When the bus is not running the only things we might need air for are converter installed devices such as a floor slide, pocket doors or dump valves as examples so we have auxiliary air compressors to provide the pressure needed to operate those. If the coach is equipped with a leveling system over ride such as provided by some converters using an HWH system or a system such as Liberty provides some may want to use the aux compressor to maintain the coach in a level condition, but if the suspension did not leak there would be no need. As a practical matter most aux compressors are not set at high enough pressures to do an adequate job of leveling anyway.

That’s the long answer. The short answer is you can leave the aux compressor off until parked, and even then you may choose to leave it off unless you have some devices that absolutely need to have air pressure such as slide room seals or dump valves.

[Tom]

Thanks for the detailed reply Jon. I had been seeing so many references to “aux air” and the suspension that I confused it with the convertor installed aux air compressor. This clarifies it well for me.

Chris

[Davy]

Alright I just put in a new Viair replacing my 350c with the indusrial and stronger, 450C 12 volt 19 amp 1/4 hp max working pressure 150psi max CFM @0 1.66 CFM Mac CFM @ 150psi .72 CFM Maximum duty cycle 100psi at 100%

You can buy a rebuild kit for about $70 but I wanted faster air less run time,

Minutes on /off & 100psi continuious ,

It runs allot less But I know these dry compressors get very hot and heat kills them so I mounted a Marine bilge blower (they are round and move allot of air with very little amp draw) right on the end of the cylender head which kicks on with the pump,

I always check for air Leaks when I am not doing anything but those little burgers Like to rear there head when the Tempeatures drop down then i dont want to go out .)

Anyway My aux pump runs my floor slide , Aids in keeping bus level if needed, Runs the toilit, runs the bed lift (which My Wife is in and out allot) belt tensioners, all the air bags on the genertor, the front bumper is Pnematic etc etc

So you have a 2 gallon tank and severel hundred feet of air line 🙂

I just found my air bags on the generator were good but all thequick connectors were leaking went to( ferrel fittings) fixed three of them today Usually my Aux pump might only run a couple times a day but it has been comming on about every half hour so for now its shut off, The good side is the new pump only takes about 45 sec to completly fill the system from empty and before the pump was so hot it would scald your hand now I checked it with my heat meater and its running about 105 Deg, at the end of a full cycle,

You can imagine in an XL in the summer or heat what the temp is inside the lower stainless door under the drivers window even before you run a compressor,,,,,

Anyway I think it will extremly increase the life span of the compressor and I like running off the 12v system,

I would show a pic but I dont know how,

Anyway next week back to chasing aux air leaks, I put the hwh Auto leveling system in manual and it holds good, So the leak isnt there,

[Archived]

To Larry and all the leak chasers………..

Larry’s remark about the bus sitting indicating the leak is not in the suspension is correct. But everyone should understand that when the key is OFF even if the suspension had a big leak, all that would happen is the bus would lean or sag down, but the aux system air pressure should remain constant unless his automatic leveling system is engaged. If the automatic leveling system is OFF it does not matter if the suspension leaks because the Norgren valves that “lock” the air in the suspension, also block air flow from the aux system into the suspension (key OFF).

Further, the coach with a perfect suspension system can sit at a given height forever, even if air is drained from the auxiliary air system. The important thing is to understand how the air systems are set up and how they function when chasing leaks.

[AL]

your right on the money Jon, I shut off my aux air pulled the airline off the gen and the Gen, bags dropped and took a little awhile to drain all the air from the aux system but didnt effect anything else,

I am taking time off for christmas the back to air leak hunting and finish the back line on my generator I saved the worst for last .)

[needtocamp]

My unit does have an aux tank. Are the air systems of aux air and engine air parallel with each other? I did see the comment about the check valve on aux air from accepting over pressure from engine air.

[JIM]

Jeff,

Yes the aux and engine driven compressor supply air to the same tank and most do have a check valve. Keep in mind, there are differences in the various conversions, so your setup could be different then others.

[David]

Jeff,

One thing everyone needs to clearly understand is the air system(s) on our coaches because our safety is dependent upon everything working as designed. To specifically answer your question every Prevost, seated or conversion, has an auxiliary air system and it is in series with the primary and secondary brake systems.

Air from the compressor (engine driven) provides pressure to both brake systems simultaneously, and after reaching a pressure of around 75 PSI air begins to flow into the auxiliary air system.

Within the pneumatic system on our coaches will be various protection and check valves so that air loss within any one of the three portions of the system will not deplete air from the remaining two.

The only use of the primary and secondary brake systems is for braking. The auxiliary system provides air for everything else. The suspension is the main use of auxiliary air but it is also used for belt tensioners, door locks, air horns, etc. On conversions air is used for a variety of other purposes such as the floor slide, pocket doors, dump valves or generator air bags. Most conversions have an auxiliary air compressor to maintain aux pressure when the bus is parked.

On this and other forums a lot of posts will deal with the pneumatic systems which initially seem very complex, but with some effort they can be seen to be actually quite simple.

[Bryan]

I’m dredging up this old post because the aux compressor has been removed from my bus and I am looking for the right one to replace it. Our entry door is air operated and we have the HWH air leveling, so the aux is really necessary. According to the scant documentation I have, the bus originally had a Jun-Air so based on the helpful posts here, I will just get one of those to replace it. Anyway, in reading all these posts I was intrigued by Jon’s comment that when the engine is shut off, the air suspension is locked, keeping the bus level. However, we have all seen old buses parked at the repair shop leaning in various directions and mine starts to lean at the front left after being parked for a few days (a problem I never had on my other coaches). I want to fix it. Am I correct that the lean indicates a leak either at the Norgren valve for that corner, the airbag for that corner, or the line connecting them? Thanks.