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No air bag charging problem?
I started the coach this morning getting ready to take a trip, everything was going fine until I switched out of level low at which time nothing happened. I have air pressure for the brakes, all pressures are good on the gauges, but no air in the auxiliary tank to charge the air bags. When I switch level low on and off, the light goes on and off, I hear a solenoid clicking, but no air in the auxiliary tank. It has been sitting for a little while and I am expected to be somewhere tomorrow. Any direction to lead me back to a checking point would be greatly appreciated. The tag axle air lift is not operational as well as I guess it is part of the accessories side of the system?
Richard
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6 Replies
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If I were to guess I would say the problem is air is not getting past the protection valve. On your rear bulkhead in the steer compartment is a valve that will not allow air to pass until the pressure on the inlet side is about 75 PSI.
If that valve starts sticking, usually due to corrosion from moisture in the system and it does not open then the aux air system will not pressurize or if it does it will pressurize exceedingly slow. Try tapping on it with a small hammer.
Does anyone have a picture to post showing the valve?
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On my 91 XL had a simular problem. Wouldn’t raise. Can you manually raise it? On mine you could. Raised it and took it in to shop. They (Prevost) said/replaced the ride height valve. All worked after that.
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I have looked for something like that, but have no idea what it looks like, therefore, I am blind poking. I have even tried looking at the pneumatic schematics to try to trace it down, no luck as of yet, thanks Jon.
I have no response to manually charge the system with the buttons, they do nothing, my accessory tank is not getting charged from the compressor, I have air for brakes, it is definately isolated to the accessory side that supplies air to the tank in the driver compartment. I even charged the tank with an external compressor and everything worked properly, but when the air was exhausted I was back to square one.
I would appreciate any pictures for reference or additional guidance and appreciate the help.
Richard
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Jon,
There is a pressure relief valve the is attached to the side of the front air filter that has airlines that lead to the accessory tank. It has air pressure on one side of it, but the air filter has no pressure. There is a knob and a compression screw on the top, I would assume it is to adjust the pressure relief point. I am thinking that this may be the issue, but there are other air lines that lead away from it and wonder what would happen if I took it apart. I just wonder whether this is a common part to air systems or if it is Prevost specific? I would like to find it around here in Houston if so.
Richard
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Disregard, I found that the pressure relief was corroded in place, I took it apart, cleaned it up, greased the internal parts back like they were, eassembled it and the accessory tank is filling with air again. I am going to find a new pressure relief valve and change it out when I get back next week.
Thanks for the suggestions, it made me go out and retrace the lines and logic, I had gotten frustraited and lost my focus and you helped me rethink the valve on the bulkhead……
Richard
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Richard, I can only suggest that your blockage is prior to both the Prevost aux air part of the pneumatic system and the converter part of the aux system which is why I have suggested the protection valve.
To find where the pressure starts (or ends) you have to crack some fittings until you get to the point where you have pressure on one side of a device and not the other. That isolates the blockage. On my 3 coaches the protection valve (which I still suspect) had a plastic label marked converter or converter air. That label was at the protection valve and indicated a point downstream of the valve where the converter could tie into the system. Maybe you still have that label or tag, and if so that the valve.
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