[Dale]

I have used a Jun-air brand in two Prevost buses. They are quiet and run on 120v. My recommendation is to contact Coach Worx in Clearwater Fl. for the latest model number and source. Ask for Rick May or Mike Bell.

[AL]

The Jun-air compressors are great. They come in a variety of sizes, are quiet, almost without vibration and often run 15 to 20 years in commercial applications. Common uses are medical and dental applications due to the discharge air quality.

You can get a new one for around $1000 or buy a good used one on ebay for around $200. Buy it, change the oil and put it in your bus. The one in my bus will pump the aux tank from 0 to 100PSI in around 5 min.

[John]

do you have any idea what model i bought one but it look so small for a better word, has a air tank about the size of a 1 liter bottel pumps up to 125 lbs in 15 seconds wasessor a dentist compr

[Larry]

Why aux. compressor? Does your coach not build air enough or fast enough for you. Air up tires, etc.?

[Archived]

Aux air on our coaches like a lot of other things varies with the conversion and how the owner uses the coach and wants it equipped.

All of us use auxiliary air on the Prevost chassis in our suspensions. We don’t need aux air to keep the coach from leaning, but having aux air on some coaches will allow a degree of leveling without starting the engine. We also use aux air for belt tensioners, front door lock and the driver’s seat. Most use aux air for the small air bags under the generator and other uses for aux air (depending on vintage and converter) include the wipers, air horns, step well cover, pocket doors, bed lift, dump valves, forward shutters, transmission retarder and stabilizators. Coaches with slides need aux compressors because the inflatable slide seal keeps out moisture so aux air on slide coaches is not a luxury but a need.

Some aux compressors are not capable of developing enough pressure to air up tires, but there are often enough air operated devices to justify having the aux compressor.

[Archived]

Thanks Jon for the reply. we are never in our coach over a couple days and was wondering.

glen

[Tom]

I put the jun air in mine a 120v you cant hear it run but when the engine air over powers the jun air it forces air back through the jun air. I am installing a check valve tomarow hope it solves the back flow. My old compressor was an older piston type in tire compartment if you flushed toilet you were probly going to wake up any one sleeping on the fold out bed up front, it was noisy and you could feel it. The jun air, if you dont see the green light on it you would not know it was running , I just hope it pumps enough volume.

[Archived]

Repoer……..If I understand you correctly about the engine compressor pushing air back through the aux compressor I suggest you do more than just add a check valve. I would suggest you verify the aux compressor is installed so it is not providing an open path from the primary or secondary brake systems.

Every compressor has a means of restricting back flow so I find it very odd that air from the pressure side downstream from the compressor is flowing back through the compressor. I’m not saying a check valve is a bad thing or is wrong to install, but I would verify all the protection valves and check valves built into the Prevost aux system are functioning, and I would insure the aux compressor has been installed on the converter side of the aux system.

You can pull up your pneumatic diagrams via the publication link in the articles section.

[Ed]

Jon thanks ill check the diagrams and see whats what .I put the check valve in today and set my aux compressor to start at 25 psi and stop at 48 psi . If I understand correctly the aux air compressor fills the aux tank in steering compartment that is used to flush toilet, door wedge lock, stept well cover slide, and possibly something else , I have no pocket doors or air bed lift, I not sure what else may be operated by it. When i bought the bus the previous owner told me he had removed the 12 volt aux compressor and installed a new 120 volt in the cavaty behind the ft bumper, it would turn on about every 15 min and was noisy and vibarited the floor ,not good .When I decided to repair this I saw that it was one of thoes compressors that oil less and used for blowing up lawn mower tires, the reason for the frequent start was the rust pin hole in the bottom of its three gallon tank,. Well it came out and Jun-Air is in They had an airline that went to the aux tank drain from the old 120v drain this put air to aux tank . They had the main regulated feed from the 120v compressor hooked to the line that (i think was the preasure line to fill the aux tank) and when i start the bus it develope preasure that i think was blowing through the 120v compressor and flling the aux tank by way of drain line, Now heres how i have it out of new comp with a check valve on at 25 off at 48 no regulator goes to a T preasure line from supply goes to T and the line supplying the aux tank goes to last spot on T. This way with no supply from engine it will have 25 to 48 psi from junair when engine is running the aux will not run because the preasure in the aux tank is well over 48 psi seams to be working but im not sure were my supply lines comes from it appears to go up to drivers area by driver seat. My bus is a 1994 Vantare my firs Prevost aways had Wanderlodges but aways wanted a Prevost .

[John]

I had trouble following the description but it sounds like a previous owner added an air line for convenience and did not recognize how or why to properly install the compressor.

[AL]

I don’t understand the pressure set at 25/48. The air toilet, if it’s a Microphor, needs 60 psi. I’ve always set my compressor at 70/100.

[gary]

I did not know it needed that much the compressor i took out was set at 35/50 and worked fine just noiser than heck. I also dont belive it was installed properly by the previous owner i have not yet look up the drawings but will soon Thanks my floor side is set for 40 psi i dont know about the door lock ot toilet.

[James]

I am un able to locate the diagram that showes how and where the air lines are run also how large is the stock aux tank mine is about 5 in around 2 foot long sound wright or has it been swaped

[David]

Different vintages and different converters had different air tank set up. My first coach had an aux tank in the steer compartment, and the next two had the aux tank over the steer axle. All of my coaches had a port on a valve assembly labeled “converter” which was where the converter could make all of the converter aux connections. Cutting into the aux system ahead of that point is a no-no.

It took me a while to learn the magic to pulling up pneumatic diagrams for my coaches but not that I know how I print “tiles” and scotch tape them together to make a very large diagram that is easy to read and follow. I think you might be able to buy one from Prevost. Not sure on that. The diagram will show the point at which the Prevost aux system and the converter’s aux systems can be connected.

If you never turn on the Jun Air all of your pneumatic devices are going to see the full aux pressure unless the supply is regulated so set the Jun Air pressure at whatever makes the devices you need when parked operate properly. Less than bus pressure is OK because it is easier on the Jun Air, so let your system requirements (such as the toilet) dictate the pressure range.

If you want the aux compressor to be capable of leveling your coach then it needs to have a cut out pressure of 120-125 which is the bus compressor cut out pressure.

[Bob]

Thanks that is what i was thinking but did not know you needed that much psi to level .I also agree that would be tough on the jun-air to keep up 125 psi the way i have it is the prevost system has over 48psi my jun-air will not run have not tried toilet yet but if i need 60psi ill raise to on at 55 off at 65 hopefuly that wont work the little comp to an eariley retirement .. Do you mean that the level low requires 125psi or the regular supension ? I still have a leak if i dont use level when parked in a day or so the drivers side will drop a lot.Im realy trying to get things right want to go se my brother in Derry NH and other one in Southwick , MA first of Sept. Your advice is mind opening and I thank you for it.