Auxillary Air Compressor

[dale farley]

I've read some of the previous posts about auxillary air compressors. Does anyone know if I should have one on my 93 Marathon? If so, where would it be located?

[Coloradobus]

Roadruner,

Take a look at your breaker panel in the bedroom to see if you have a breaker labeled, "Air Compressor. If it labeled, it maybe behind you front bumper. Anothe place to look for an air compressor, is on top of your generator, that is where Marathon placed air compressors in later years.
Do tell what you find. I shooting in the dark here.

[mike kerley]

Our 93 CC has it located behind the generator, second bay. Access through a small hatch in the first bay, drivers side. Ours has a power switch in the first bay marked "aux air compressor". 12 volt item. To work on it, I pull that section of the bay wall out.

Mike K

[jello_jeep]

Mine is mounted on the generator, have seen lots of Marathon's with a smaller unit mounted in the "shoebox", an area hidden by the lower door under the driver's window.

I had spoken to one chap who said he had to replace that small one every 1.5 years or so, and actually carried a spare :confused:

[dale farley]

I will check out these places in the next couple days. My coach is at a friends house at this time. I probably didn't ask the right question to begin with. I am reasonably sure I have a small compressor for the accessories such as the step slide, etc., but according to my manual, the compressor for the accessories is not connected to the air bags.

I saw some posts that said you could run the compressor to level the air bags if they were down. I am not sure if I have any way to do that without starting my engine?

[dalej]

Dale if you have a aux. compressor that is plummed in the aux tank of thr bus then you can level the bus, that is why they us aux air. some comvertors like marathon 96 time frame didn't use them but its not that big of deal, you just add one yourself. The idea is so you don't have to stat the bus to level the coach. I have Level Low.

[Jon Wehrenberg]

If your coach does not have an aux. air compressor in some respects you may have an advantage.

Certain coaches that have aux compressors do not have sufficient aux. compressor air pressure to level a coach, so starting out having to add one allows you to make certain the one you add can do the job.

Every coach varies because the converters have different axle loadings. For example a coach with a generator near the front, especially a 40' coach, is going to need a lot of air pressure (probably around 120 PSI) to raise the front of the coach.

Conversely, a coach with the generator towards the rear on a 45' shell, may only require 95 or 100 PSI to raise the front.

Without making a big science project out of it you can determine how much air pressure you require by letting the bus air pressure drop to about 80 PSI, and then using a portable compressor and a regular tire pressure gauge put air pressure to the bus and check the pressures as the front raises. Each increase in height requires more pressure, so monitor the pressures along the full travel.

For those who already have aux compressors and are having trouble getting the front to rise, you can cheat a little by picking up the tag axle. That takes a little weight off the front axle and will allow the air bags to extend a little further. After you mess around trying to level your coach that way however, you will come to the conclusion it is a whole lot better to just fix the leaks.

[MangoMike]

A HOW TO: to add an air gauge to monitor your Auxiliary Air Tank.

http://www.prevoman.com/Pages/Aux%20Gauge/Auxpg1.html

mm

[win42]

Air Compressor Selection: At POG2 some of us ran down to Home Depot and bought a 110V compressor to use as a tire pressure portable unit. I have been toying with the idea of piping from it's temp. storage location to the Aux air location and use it for aux air suppliment. It usually takes overnight for the coach to drop the front end. The rear does not dop. No Jon, I have not found the air leak yet, but I will continue to look.
I'm hooked up to shore power 99% of the time when parked, so I don't think a 24V compressor is manditory. If you boondock a lot then yes it would. Mike; adding the pressure gauge was a good move. If I follow the course described above I will add a pressure regulator to the line to avoid adding the 145 PSI the compressor is capable of to the Aux. air system. "Stand a back it's a biga dange!" I don't want to add fuel to the little glowing problem I allready have.

[MangoMike]

Big Harry,

If your leaks are relegated only to the front end you're in luck, so to speak. I believe all the Norgren valves are up front with 2 or 3 in the steering bay. Start w/ blasting those suckers with your high tech soapy leak detectant and see if anything arises. It just may be one of those up front norgrens. Worse case it's the ride height valve located in the center between the wheels over the axle or possibly a leaky air bag(s).

Let us know.

The War on the Leans continues...

mm

[win42]

M Mike: I put new kits with new o rings in all four Norgren Valves. No change I'll check the lower air valve. If it's the air bags I don't want to know. What about other things as door slide, wipers etch.? I'll keep on checking until the culprit shows it's ugly head.
Thanks Mike

[MangoMike]

Jon will correct me if I wrong, but the level low system is a closed system. So that unless you are raising or lowering the palace the norgren valves should "lock" the air into the air bag system. Door slides ect should have no effect on the bags.

Someone please correct me if this is off base.

mm

[Jon Wehrenberg]

Harry,

Mike is right. He gave you all the good news there is. Whatever is leaking to cause your front end to drop is almost assuredly related to the areas he listed with one addition. Your valve pack located on the rear wall in the steer compartment could also be a contributing factor, although if these leak it is generally against the Norgren valve actuator.

If you do not see anything, get a means to listen such as a stethoscope or an ultrasonic leak detector. Here's the bad news. The leak could be in the cannister at the bottom of the air bag due to corrosion. A leak that takes all night to drop the front is not very big, so soaping the entire base of the front air bags may not show the leak. Also. Roger had an air bag leak, but it was on the inside towards the center of the cozach and he had to get under it in between the wheels to see it.

There are also numerous possibilities for aux air system leaks also, but if you solve the front air bag problem you can then deal with the others.

I believe Royale used the Prevost Level Low system without modifying it.

When you worked on the Norgren valves did you bench test them?

[MangoMike]

While checking the "air worthiness" of my new Aux. Air Tank gauge, I discovered this leak in the converter manifold.

602

Is there an easy fix to this problem. I don't think you can tighten the coupled 3 ways any more.

I can't believe the number of places that can leak on a bus. But I'm going to discover them all.

Mike

[Danss]

On two different occasions I have been checking the tire pressure and when removing the guage the air kept coming, This is my 2nd bus this has happened on, and it happened today on 2 different tires. Thank goodness for Good Sam. Does anyone have any suggestions on how to keep this from happening? I am now afraid to check pressure unless I am near a tire place. You sure:mad: do get a sinking feeling to hear that air pouring out. Dan

[truk4u]

Danss,
Do you have Equal in your tires? If so, they should have had different valve stems and core, Jon can jump in here. The little grains of equal get stuck under the valve seat and leak air. I had this problem on a CC and had to shoot a little air back in each time I checked the pressure to keep them from leaking.

[MangoMike]

Those little cores have a small filter in them to keep the equal out. The problem is they are longer and will not fit the curved stem on the outside drive wheels. Now if someone knows of shorter ones let's get them posted.

The other option is to have your own air hose hooked up to the aux air nozzle in the steering bay and blast the equal back in the tire like Tommy truck was saying.

http://www.prevoman.com/Pages/Aux%20Gauge/Gaugecover_3682.jpg

I've also found that sometimes you can get lucky and keep on jabbin that air guage back on the valve on sometimes it will stick closed.


Mike

[bill&jody]

i've noticed that the aux air runs more in cold weather than hot. here in fla, it runs every 2-3 days. when we were in 20-40 degree weather (yeah, we did fall in vermont) it ran 2-3 times in a 24 hour period.

got any hot ideas why this might be true?


wmm

[Jerry Winchester]

Bill,

Seems everything leaks more in cold weather due to the metal contraction. When our coach was in the hanger this summer, it never leaned. Not a drop. When we brought it back from Oklahoma, it was cold in Houston (38-40 deg) and it had the leans in a day.

Same with our aux compressor. After I fixed the toilet air regulator leak, it runs very seldom. In the cold weather, it runs more often, just like yours.

[bill&jody]

jw-
interesting....
i don't seem to get the leans, so that would indicate (to me anyway) the leak is up forward in a common line. but i ran the old boy up on a stack of custom cut 2x10s (gets about a 6+ inch lift - enough to keep from squishing me like a grape if i break a line while tightening it). i don't think i have any leaks up front (no bubbles, anyway). maybe it's got a leaky air bag, but seems that would cause a lean. are the two front bags connected to a common line? does a leak in one cause a pressure loss in both? i think you and i have the same chassis.

oh, yeah - pics to follow.

wmm

[Jon Wehrenberg]

Dan,

Tom and Mango are both right. There are two ways to deal with a leaky tire valve. The first is to replace it. Sometimes this is the only option, but the second way often works and that is to let the tire pressure bleed down a little so the air flow going back into the tire has a much higher pressure than the internal tire pressure. Sometimes this literally blows the offending piece of grit from under the valve seat. If the leak persists you do have to change the core, which is no big deal on all but the inner tires.

Bill,

I don't know why, but colder temperatures will cause leaks in the air system show up sooner. As time passes the leaks causing the more frequent compressor run time will be showing up in the warmer temperatures. Enjoy what now sounds like a very air tight coach.

[Jon Wehrenberg]

Mike,

I think that manifold that is leaking is nothing more than a stack of brass "Tees". I think you can disassemble the whole thing and reapply some plumbers pipe thread seal and the bubbles will go away. You might have a little trouble getting the close pipe nipples out, but if you ruin them they are cheap and available at any hardware store.

[MangoMike]

WHAT!

I can't order this part for $983.22 from Liberty. Bummer. ;)

ok, I'll go to Home Depot.

Thanks

mm