[Rodger]

Bryan,

For any of us to answer your question we would need to understand the MCI leveling system. I strongly suspect it is different from the Prevost system so any answers might end up being guesses.

Prevost has on line access to 100% of the technical information regarding its coaches, including wiring and pneumatic diagrams, service manuals, owner manuals and links to component technical information. I suspect MCI likely makes the same information available so that would likely be a good starting point to understanding your specific coach suspension system. I think you will find that your suspension, like ours has some type of valve configuration that allows only ride height valves to function when you are driving, but when you are parked it isolates them and enables other valves that can add or exhaust air from the air bags individually so you can level the coach on uneven sites. What we Prevost owners are unlikely to know is how those valves function within your aux air system.

I have printed out my pneumatic diagram so it is about 3 feet wide. That large size helps me when I take a highlighter to the diagram to follow the air path on any of the pneumatic systems. I enlarged “tiles” and taped them together, others have brought the PDF file link to Kinkos and had them print out an oversized copy. It is a valuable resource.

[Jim/Chris]

Thank you, Jon. One of the pitfalls of having SOB is lack of a vibrant group of enthusiast owners. I do have quite a library of the MCI manuals, so I will dig in as you suggested. There are certainly some differences from Prevost. The MCI has several computers which monitor and adjust ride height. In fact, the operators manual suggests that if the bus is ever towed, the engine should be run at high idle during towing in order to power them, even if the tow truck is supplying air to the systems. The kneeling feature is still intact on mine and MCI also has controlls that allow increasing and decreasing ride height by several inches while moving slowly to clear steep driveway aprons and low clearances. I like your idea of super-sizing the the pneumatic drawings.

Regarding the Jun-Air compressor, my documentation shows that the converter installed a Model 6, probably the motor only version since it was plumbed directly into the aux tank. Is that what you Prevost guys have? Is there any reason for the compressor to have its own tank? The Model 6 has max pressure of 120 psi, so the tank would have to be pretty big to make it useful for filling the tires, I think. They are very pricey. If anyone has a line on a used one I would be much obliged.

[Archived]

Let’s start with a question. If your engine breaks and you have to be towed how does MCI expect you to run it at fast idle while on the hook? Inquiring minds want to know.

OK, more serious now is to address an aux air concern I have heard frequently and that is how big a compressor do you need to air up the tires. The answer is you don’t need an aux compressor at all to air up tires. In fact until you get to compressors so big they are not practical to carry in the bus they are all too small unless time is not a factor and you don’t need high pressures. Just run you engine at high idle and let that engine driven compressor be your air source for tires. That is more than ample for those few occasions when you need to adjust tire pressure.

I don’t know if every conversion is plumbed the same, but on our coaches Prevost provides an air connection point on the aux air system in two places and they want the aux air compressor to feed into the system downstream from that point. The reason is that point has protection so a catastrophic loss of air pressure on the converter installed side of the aux system will not compromise the safety devices built into your bus systems. Those connection points are so important Prevost marks them with an engraved plasitc tag that identifies them as the converter air connection locations.

If you do not have a way to verify your converter tapped into the coach aux air system at such a point I would not hesitate to contact MCI engineering and ask them to identify the proper location. If the converter has connected to the right place (and I suspect it has) then you can tee into the system at any point downstream from that location. Your aux compressor will pressurize the aux system air tank provided by MCI for the suspension, other uses and the house.

The aux tank is likely the same size as the primary and secondary air tanks and is more than adequate for any purposes although I have seen conversions with added aux tanks or even compressors with integral tanks. I would be reluctant to add a tank unless I knew it was built to the appropriate standards for tanks used on our coaches. The air systems on our coach really require the best of everything due to the fact our braking system relies on a good pneumatic system.

[Bryan]

Yes, Jon, I had that same question about towing. The operator manual warns that ignition must be “on” during towing for the computer leveling to function and it also warns that the battery will run down quickly unless engine is running at high idle. There is no mention of how to solve the conundrum if the engine is broke. Can you say “Landoll”?

I understand that the aux compressor inlet was plumbed correctly as you describe, but will confirm that before connecting anything. Right now my challenge is finding a compressor. Thanks as always.

[Archived]

Bryan, where’s your air dryer? My last coach was a plastic 42-foot Beaver. The air dryer was conviently located in the rear on one side. Beaver extended a line to the front of the coach for towing witha chuck any and shut off valve. Really, a pretty smart idea. A friend’s coach of the same model was being picked up be a wrecker that does a lot of coaches near Tampa. I told the operator of the connection point and he said we really like to hook up to the dryer and he did. On a Prevost that would be a PITA, so we have the connection point in the engine bay. If your dryer is readily accessible you don’t need anything else.

[Fred]

Thanks Gil. Unless the converter added a line back to the dryer, the only inlet that goes through the air dryer is in the right rear compartment, as on my old Prevost. There are inlets in the compartment under the driver seat for filling the system and applying brakes during towing, but they do not go through the dryer. (see picture). I assumed the now missing Jun Air compressor was plumbed to one of those inlets, but there may be other air lines that I did not see. According to the manual, there should also be schrader valves in this area that can be used to fill the primary and secondary tanks. I haven’t looked at the connectors closely, but they may be the bottom two. This is a photo I snapped before I even realized there should be an aux compressor in this compartment. I’ll have to spend time this weekend getting it figured out.

A new Jun-Air compressor model 6 is $1335. Ouch.

[Archived]

Bryan,

Are any of these what you are looking for? http://www.ebay.com/sch/?_from=R40&_trksid=m570&_nkw=jun-air If you happen to be in the Sarasota area I know of one in a pawn shop there as well for a reasonable price.

[Archived]

Thanks, Alvie. One of those is right. I checked ebay yesterday and did not find it that one. This is really great!

[needtocamp]

Bryan,

For those of us with few aux air demands while parked we often have a run of the mill small compressor like you’d find at your local big box store. Similiar can be found online that are a bit quieter. If yon can find the Cadillac, it’s okay to use a Chevy for this application. Some even have DC powered compressors. Personally I’d stay with an AC powered one.

[Archived]

Will a jun air of312 compressor work for the aux compressor, its the suitcase type/ oil-less. Would the oil-less be better or will it make to much noise. Will compresors that take oil get into the seals, valves and cause problems?