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For those with an Aux Air gauge?
How much does your aux air normally vary?
My 94 Angola conversion never had an aux air compressor or dash gage until I installed one this month. Today I made my first trip with the new gauge. It varied from about 90 to 115 psi when running down the road (aux compressor off). It was rarely steady. I expected it to vary as the ride height made adjustments so just wondering what others see on this gauge.
My aux air system is fairly tight. Pressure will drop about 30 psi over a 12 hr period. The aux system only has the step slide, door lock, and air horn connected in addition to the suspension air. My generator air bags have to be filled manually. Sitting for about 7 hours and the aux compressor has run one time.
My primary and secondary brake air are also fairly tight. They held perfectly steady at 115 during multiple cycles of the aux air.
BTW I installed the Viair 450C compressor, moter rated for 100% duty cycle and a 85 on- 105 off pressure switch.
Thanks in advance.
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8 Replies
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Sounds about right. Mine varies in the range of 95-115.
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Good job, I wouldn’t be without the aux air pressure gauge, it will
tell you when you have a problem while driving because you never hear
the engine driven compressor cycling and dryer purge.
Your gauge pressure sounds right, although I like at least 120 on the top side.
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Tom, the front and rear or primary and secondary air gauges will tell you if the main compressor is cycling. So, you’re saying you keep your aux compressor on when driving? My aux systems stay pressurized by the main engine mounted compressor when driving. Is there value in keeping the aux compressor running? If so, is it due to some big air demand system?
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Gil,
All of us can leave the switch to our aux compressors on all the time because when we are driving the engine driven compressor will satisfy the aux air requirements and the aux compressor will never run unless the set points are above the coach pressure of 100-120 (cut in, cut out).
The aux system is supplied with air as long as the secondary system pressure exceeds about 75 PSI.
There appears to be some confusion regarding aux air and it is really simple. We must have it while driving because it is needed for the suspension which is always taking and exhausting air as we drive. It also tightens our belts, is needed for coaches with a transmission retarder, opens or closes forward shutters, is used for wipers on older coaches and the door lock on newer coaches. Because it is needed it is automatically filled with air from the bus compressor. But it will never fill unless the primary and secondary systems are satisfied.
When parked, depending on how the coach is equipped and who the converter is it may be required for a variety of purposes such as pocket doors, generator air bags, dump valves, or not at all.
The reason it is important to have an aux air gauge is if an air bag fails for example we will be able to see the issue on the gauge.
On my coach I need aux air all the time so when we use it on trips I just leave the switch on. I have the set points very low because it is not necessary to have a lot of pressure. I think my current set points are 60-80. I could probably go lower.
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Thanks everyone for the confirmation.
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Jon,
My aux compressor is off more than on. In fact it’s only turned on prior to starting the engine if the belt bags are deflated and while parked and occupied. I thought you did the same with a post a while ago were you said not to worry about deflated belt bags at startup citing the fact seated coaches don’t have aux compressor.
FWIW, the rationale for leaving my aux when not in use or driving is to reduce the possibility of it running too much from a leak and there’s no reason to produce moist air in an idle system. In my case the compressor cycles a few times a day and I get little to no water out of the aux tank drain. Still, why risk it?
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Gil,
You misinterpreted what I said (or I didn’t say what I meant). When we are using the coach, from the moment we pull out of the garage until we return I need aux air. So when we travel the aux compressor is on because it is needed for slide seals. As long as the engine is running however it just doesn’t matter if the switch is on or off because the engine driven compressor is keeping the aux air system satisfied. But when parked I need aux air hence the reason for the switch to be on.
When in my garage however the aux compressor switch is off for two reasons. First, we are not in the coach so it makes no sense to maintain air pressure for pocket doors or the bed lift or the dump valves for example. Second, since the coach is under cover in the garage I have no need to inflate slide seals either so we just keep the switch off.
On our previous coach I rarely turned the aux compressor on because we had no seals that needed to be inflated. We did need aux air for the dump valves so if the aux pressure was down when we wanted to dump I just turned on the compressor to do that. With just the two of us we rarely opened or closed the pocket doors.
As to starting up with loose belts………I do it all the time. My logic is seated buses don’t have an aux air compressor so they are started with loose belts. If it was a problem Prevost would have done something different.
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Wrong Gil… The prirmary and secondary brake tanks without a leak
while driving will not indicate the engine compressor and dryer cycles
as the aux depleats with either a leak or the suspension working. I do not keep the aux compressor on while driving, I could, but it won’t matter as the set pressure is below the engine driven compressor cut in.
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