Auxiliary Air Pump?

[ajhaig]

We've had a problem with our aux air pump, the pump will not shut off. There is a little gray box with wires and hoses near the aux pump, if I flick it (sorry to be overly technical) the pump shuts off and then turns itself on as it always has, but again it won't shut off. Prior to the problem the pump would run for about 5 min every 3 hours or so.

I was running the pump by turning it on and off manualy during the day mainly because I thought that we had an air opperated toilet. On our way from LA to San Diego we stopped by California Coach, Steve has a very similar Marathon coach and I asked him about the problem, to my surprise Steve told me that his coach does not have an aux pump. Steve then confirmed that our toilet is electric, not air opperated.

I am going to have the pump repaired next week at Marathon, but I don't understand what the point of the pump is. The only thing inside the coach (to the best of my knowledge) that runs on air is the slide over the stairs, which we never use while we are parked. I understand the the aux air helps the coach stay level when parked. Our coach stays pretty level without the pump for about 4 days, which I think is normal.

Is there any harm to not running this pump and why was it running so much?

Thanks.

AJ

[rfoster]

AJ: I am sure many others will chime in on this, but to answer your question, I will give you a run down on my bus as to the aux air supply: It supplies the bellows for the (2) fan belt, (1)air conditionion compressor, 4 air bags for the gen set, 2 pocket doors, bed lift, entry air door lock, drivers seat ride and bolsters, 2 dump valves, 1 fresh water valve, floor slide, front louver, and probably one or two items I have forgotten. Normally the aux air controls the leveling but must have assistance from the engine compressor on my bus to assist in the lifting process. Even the rear tag gets involved.

The problem with your compressor failing to shut off sounds like the pressure switch usually located in the compartment under the drivers seat. Generally a fairly simple deal to take the old one off and install a new one if you are going to the converter's shop. The cycling on and off about every 3 hours indicates you have a leak, but not severe. Don't worry it will get worse over time and will really surface.

I had a terrible time finding my worst leak with all the accessories involved, but turned out to be the bolster on the drivers seat.

[dalej]

AJ, A good test is to just leave the little guy off for now and watch your gauges on the dash. You have
two, one for the rear brake tank and one for the front brake tank. The front one feeds your aux. air
tank in the steer bay. If you notice that the air gauge on the dash is going down to about 80 #s by
morning then that is not to bad. If you have a reading about 20-60 pounds you have some leaks that
will need attention sometime. In the later case you will need a aux. compressor to supplement a leaky
system or else you will start to get the leans.

[Jon Wehrenberg]

AJ,

This should be what your pressure switch looks like. Open the plastic cover and there is an adjusting screw to lower the cut off pressure.

If it has failed these are typically found at Home Depot of Lowe's

No need to spend money to have some one do what you can do in a few minutes.

[truk4u]

Dale,

I think AJ will find the two dash gauges are front and rear brake tanks and does not show anything on the aux. He would need a third gauge dedicated to aux tank. If the aux drops to 0 psi, it shouldn't have any bearing on either brake tanks.

My Marathon did not have an aux compressor either, maybe someone added the one he has for an aux air hose. His Marathon aux system probably only runs the belt bellows and stair slide. My generator air bags were manually filled.

AJ - You should have an aux air gauge inside the steering compartment and you can watch that gauge to see if it builds air while your compressor is running. If not, the aux compressor isn't even plumbed into the aux tank.

Just trying to help or confuse, whatever works....

[MangoMike]

AJ,

If you don't have an aux air gauge in your steering bay, here's the howto to add one.

Picture 16.jpg

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

Mike

[dalej]

Just to clarify, the two gauges on the dash are for the two brake tanks. It is the front brake tank that feeds the aux. tank. The brake tanks have a check valve that keeps aux. air from feeding the front brake tank. When the aux. tank looses air it is fed by the front brake tank, so the pressure is the same. You can use the gauge for the front brake tank to see how much air is in the aux. tank since they are kind of one in the same. Just remember that the aux. tank can not feed the brake tank. There for you don't really need a gauge on the aux. tank. It's not a bad thing to have but you have to open the steer bay to check it when the gauge on the dash will show you the pressure.

[ajhaig]

I think I'm going to take a stab at replacing the switch. It looks exactly like Jon's.

AJ

P.S. People in California seem to have it all figured out... Ice skating at the beach in 75 degree weather!

[Jon Wehrenberg]

Don't be too hasty about replacing that switch. It may just need an adjustment.

Somestimes the pump is set to cut out at the maximum air compressor pressure. As the compressor ages and the bus air system develops minor leaks it is no longer capable of reaching that pressure. With the pump running try to adjust the pressure switch downward to see if it will cut off. Recycle it a few times to see if that does the trick. If not, then you can replace the switch.

If your only need for aux air is the floor slide, it is almost unnecessary to run the pump. The only time you typically use the floor slide is when you have the engine running and the aux air system is being pressurized by the bus.

Your bus should be capable of sitting level even with zero air pressure in any of the air systems. The only time you want the aux air pressurized might be when parked for a long period so you can relevel the coach, but as Roger says some aux air compressors do not provide enough pressure to do that.

[dalej]

AJ, when you undo the one nut that holds down the gray cover, remove the cover and you will notice
the contacts at one end and the adjustment springs on the other. With all this exposed turn on the air
compressor and lift on the plate that the bigger spring is pushing against. Use your finger or a small
screw driver, you should be able to turn off the air compressor by moving the plate. The smaller
adjusting nut is for adjusting the ON pressure.

If this works to start and stop the compressor then the switch is fine. It will be the leaks in the system
that keep the compressor from achieving 120 pound or what ever the cut off is. Your bus air
compressor has a huge volume compared to the small auxiliary air compressor. It just might not be
able to keep up.