[Chuck & Katrina]

Two things come to mind…

It is typical that leaks slow as the psi drops… yet, when you mention specifically 60 – 70 psi, makes me wonder if the PR-2 pressure protection on the Prevost factory accessory (aux) air tank MIGHT be leaking until it hits it setting point which is about 70 PSI.

Seems all valves do strange things at times… A couple of years ago while I had easy access to my accessory air tank, I removed the tank, removed the PR-2 valve attached to it, and re-located it to the back wall of the steering bay in order to have SUPER EASY access if needed in the future.

Here is the strange part… the near 2-year old PR-2, which is also a one way check valve, began sticking for about a week. I recognized this strange occurrence as when the aux air compress ran, it also filled (back-filled) the primary and secondary tanks.

If it continues, I will definitely appreciate having relocated the PR-2 valve from the tank to the back wall of the steer bay.

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2000 Featherlite H3-45

2024 Jeep Grand Cherokee

Leesburg, FL

[Art]

Jeff:

I hear what you’re saying but, my brake tanks are holding at 120 PSI so the aux tank can’t be leaking back.

Chuck

[Clint]

Yes it can. It leaks into the main supply line and back thru the compressor

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Clint & Tammy Summers
2000 XL 45 Country Coach (rivets)
1977 FC31 Bluebird Wanderlodge (more rivets)
Vonore TN

[Jon]

A leak back due to a failed or leaking check valve needs to be repaired. The easiest way to monitor the brake system condition is to drain the air tanks in sequence, starting with the wet tank. Each tank in succession should remain pressurized.

If not, it is important to fix it.

[DON]

Hello Jon – in a Liberty configuration, would I be correct in that the 120 vac aux air compressor psi setting “switch” is the “pressure switch”?

Wondering if it can leak / leak backward….?

Seems if it were leaking backward, the Liberty install Parker spitter air water separator valve would be leaking out of its bottom drain…?

Is this correct? Wondering if the Liberty installed GAST compressor can be an accessory air leak point? (and how)

THANK YOU!

[Chuck & Katrina]

My guess is YES a leaking normally closed check valve will allow aux pressure out and thru the aux compressor back to the atmosphere.

With my Liberty the aux compresso air passes thru 2 SMC air/water filters/traps, then thru a 120vac Versa brand normally closed solenoid check valve, then pressure is sensed by a SquareD Pumptrol 120vac adjustable pressure switch w/pressure relief.

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2000 Featherlite H3-45

2024 Jeep Grand Cherokee

Leesburg, FL

[DON]

Hummmmm:

So it could leak back through the main line and out the compressor with out affecting the brake tanks. Will have to go down that road and see where it goes.

Jon:

Have done the drain down test per your suggestion, safety valves work. On a side note; before I replaced my brake relay valves and had a slow leak down on the brake tanks the Aux tank would drain down to zero with the brake tanks. Since replacing the brake relay valves I have basically no brake tank leaks, just a slow leak in the Aux tank.

As noted, brake tanks stay at 120 PSI for months before slowly leaking down further (maybe 1/2 PSI a day if that). Aux tank will drop to around 70 PSI overnight, then take another 4-5 days to reach zero while the brake tanks remain at 120 PSI.

The leak is in the Aux and is small enough that it’s not a priority to fix but more a challenge

Chuck

[Gordon]

Here is a thought for you! Your wet tank has no check valves, If your wet tank drops because engine air bags- compressor governor- regulator and red knob valve for engine belt air bags. The wet tank should be the same pressure as aux tank till 70 psi because protection valve on aux tank supply then if it is wet tank aux psi will stop or slowly drop. While driving watch aux gauge if Primary and secondary tanks are holding and aux gauge ie going from 100 psi to 120 psi every few minute’s then check wet tank. Pull up your air schematics and follow the air

[Unknown Member]

Chuck, Don is right.

If the accessory system loses air unless something is wrong with the systems the brakes are unaffected.

And yes the accessory system can leak back to the compressor or forward to the various devices. The Liberty conversion never ever uses brake systems air for house purposes.

The accessory system is a combined Prevost and Liberty air supply, such as suspension and other Prevost systems, as well as pocket doors and floor slide and other Liberty systems.

I presume other conversions are set up the same but that is a guess.

[Chuck & Katrina]

My Country Coach is the same, i can bleed down everything Aux related and my brake tanks remain at the same constant pressure when i started. The only way to get my Brake tanks to drop is to push the brake pedal.

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2000 Featherlite H3-45

2024 Jeep Grand Cherokee

Leesburg, FL

[DON]

I know of one Aux air leak that’s probably never going to be fixed. The sliding door to the bedroom has an air cylinder that’s going to require the washer & dryer on one side and the refrigerator on the other side be removed to remove the door air cylinder for repair. Not worth the effort. I just put a shutoff valve in the line and turn it off when not traveling down the road.

My aux tank stays up when driving, I do need to check the wet tank and governor for leaks. The system is not leaking much right now so my incentive is low. LOL

Chuck

[DON]

@Don
This might be a stupid question, but in your post above, the first picture shows the “120vac Versa brand normally closed solenoid check valve”.

Given that it’s normally closed (to keep air from bleeding back to the compressor) and assuming when the pressure switch turns on the compressor it additionally opens this valve ‘electrically’ – what functionality does that provide verses a standard passive check valve?

[Jon]

The SquareD Pumptrol 120vac pressure switch is “adjustable”.

I keep mine adjusted to turn on (close the 120vac circuit) at 30 psi, and turn off (open the 120vac circuit) at 60 psi.

This works for me & my bus and its aux system accessories.

[DON]

I understand the adjustable pressure switch, but what about the electrically operated solenoid check valve right in front of it. Why couldn’t that be just a passive check valve?

[Mike, 92 Country Coach]

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