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aux. compressor
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Jon, I checked the valve…it’s open
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If the red valve Don pictured is open, and the bus has been run so all air systems, especially the accessory system have been aired up, and the belt tensioning bellows or mini air bags are not tightening the belts the reason air is blocked has to be investigated.
The air supply to those belts is not on a converter portion of the accessory system. It is a Prevost chassis system and when you have air to things like the suspension and other Prevost chassis air operated functions your belts should be tight.
Operation of the aux compressor is not going to solve that problem if that problem continues, and in fact is relatively unimportant until you can get your belts to tighten. You do not need an aux compressor, but you do need tight belts on the engine.
Do you know if the engine driven compressor is pressurizing the coach accessory system? From a low or zero pressure start on all air systems no air should flow into the coach accessory system until both braking systems reach about 75 PSI, at which case a protection valve opens and allows air to flow to the accessory air system. Can you verify the accessory system is being pressurized?
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With the engine running and you’re not getting air to the bellows, I would suspect the regulator mounted in the engine compartment.
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I started the bus and let it run on idle while it built air. I have to admit I did not let it run until the air built all the way up and I’m not sure now how much pressure there was before I shut it off. I just know it was above 60lb. I’m going to try to start it again and let it build up to max…Thank You
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Thank You Jon!!! I let it build on idle to max and the belts are tight!! mI feel like an idiot but I just didn’t know the air had to be so high to make things work….Again…Thank You, That’s one problem solved anyway
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When you here the air dryer sneeze, all systems will be full.
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Thanks Don!!
1999 XLV X-6872, liberty #440 -
Steve, this has added a little knowledge of your understanding of the coach pneumatic system, but I don’t sense we addressed your concerns about the aux compressor, and in fact it sounds like that is a remaining issue.
Assuming it is not functioning make sure the switch in the electric panel that is labeled “air compressor” is on and the green light adjacent to it is lit. The green light verifies power is getting through the switch which is also a circuit breaker.
Pictured above is a grey plastic housing for the aux compressor. Some have a switch on the side. Verify if it has a switch and that the switch is in the “on” position.
The accessory air system pressure has to be low for the pressure switch to provide power to the air compressor so make sure that pressure is very low, perhaps as low or lower than 20 PSI. Those switches are adjustable so it is possible a previous owner set the pressure to a very low value. If the compressor does not come on and if you are comfortable playing with 120V AC electric power, remove the pressure switch cover and verify power to the pressure switch and continuity through the switch to the compressor. If power is in those places it is probable the compressor is bad.
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Steve,
On our coach, I have a port on my regulator with an air chuck fitting next to my red valve, like in Don’s last picture. I could add air to the engine bellows from there if needed.
I also installed a check valve in the line to prevent a leak from there affecting the rest of the system.
I also have a fitting inside the curb side engine bay door attached to the air dryer drain valve that can be used to add air.
On my coach, the fan does not run until the engine is up to temperature or I turn on the dash air conditioner. The air should be built up way before that happens.
Next time before you start your coach, fan the brake pedal to drain the air below 60 psi. Then start the coach, your low brake pressure lights and alarms should be going off. Take note of the pressure when the alarms and lights go off. This should be part of your DOT brake check before every trip.
Listen to the valves open and your accessory tank start to fill around 90 psi.
At the same time, you should feel the air start to flow into your seat.
Like Don said, listen for the air dryer to sneeze at about 120 psi. This means the engine compressor pressure switch has been satisfied.
Your engine bellows should be full and your belts tight. If you have a guage in your red valve / regulator set up like Don, take note of the pressure. I believe it should be about 50 psi.
Take care not to get tangled up in any moving engine parts while you are looking up and backwards in that tight space.
I am sure you are aware, that the two doors below the drivers window are kept closed by their own keyed lock and the two large flat head screws, one at the top and bottom of each door.
On our coach, I can access that compartment through the drop down front bumper too.
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Steve, if your belts are becoming lose after sitting, the check valve attached to the red handled valve could be the culprit. Check the archives as Boater Al has replacement valve numbers and photos in several posts. Welcome to the jig saw puzzle called Prevost Conversions.
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Most often Overlooked check valve. I think this is the one Triple Fox is referring to.
With replacement of pictured check valve plus good mini air bags and hoses will be rock hard forever.
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Except for the crappy push in hose fittings, the lousy leaking regulators, the leaking red handled valves…………
If only all it took was a check valve I would still have air bags for my belts.
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