[Archived]

Aux air compressor will have a breaker in the load center. Compressor on turn key on without starting, does that show air pressure to the belts? You can start the coach and leave on low idle until air pressure gets to the belts…

[Harry]

yes, it’s on but compressor not running

[Frank]

I can start the coach with the belts loose like that?

[joel]

Aux Compressor breaker at the load center: ON

Key turned to: ON (just before you engage the starter)

Compressor doesn’t run? Fill up the engine belt bellows with air and tighten them?

Do you have a Liberty Elegant Lady (24 volt coach) or a Liberty Class Lady (12 volt coach)? What about your other Liberty installed air features like the air lift for the bed? Air operated pocket doors? Air assisted toilet? Air operated dump valves? If you have those air operated features do they work?

The short answer on starting with the belts loose … yes, but as Jeff directs you use low idle. Once the coach starts to build air off the Detroit Diesel, the bellows should fill and tighten the belts. Then you can go to high idle.

Your name, year, chassis type, converter, and converter model in your signature will us help you.

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1999 XLV X-6872,  liberty #440

[Billy]

I’m not sure. It has the air lift bed, air toilet, and switches for port dump and bypass valves but they don’t appear to work. I do know it has both 12v and 24v in it. does not have air pocket doors. It has a manual by pass lever near the outlet hookup but has a switch by one of the sinks that I don’t think works.

[Andre]

thank you all for the information, i went back to “my profile and don’t see how to put the info on my posts like you folks have it. My name is Steve Comes, Pemberville Oh. I’m not sure witch liberty I have but it’s coach#373.

[Archived]

Steve,

You are at this point where almost every one of us was when we got our first coach. One huge benefit you and other new owners have is PC and the internet.

Unlike the government, we really are here to help you.

Start to help us help you by adding a signature line. Knowing some specifics about your coach will allow some specific and more accurate responses. Then if you add your location we may actually have some experienced members near you willing to be available for show and tell.

But to address your initial post, Jeff did give the answers. But you may have issues so I will provide a bit of an explaination. As Jeff said, start the bus and let it run at low idle until you get some accessory system pressure. If you do not have an accessory system pressure gauge (only two brake system gauges) you know you have pressure when the driver’s seat rises. More on that topic later.

When the bus accessory system has air the aux compressor may not run. So if turning on the key did not tighten the belts you can assume the accessory system had little or no air so the second answer is you need to deplete the accessory system air by turning off the engine, turning the key back on and using the leveling system dump air from the air bags in the manual position, and then fill the air bags until you can’t add or exhaust air from the air bags. That will drop the accessory system air pressure low enough to cause the aux compressor to come on.

As Jeff mentioned the switch is in the electrical panel near the kitchen and if you are getting power to the circuit a small green light next to the switch will come on. If the compressor doesn’t run it could be a bad compressor, or your pressure switch for the compressor in the steer compartment may have a switch on it turned off.

As a new owner you have a lot to learn and do not hesitate to ask questions. Not a single person that owns a Prevost knew anything when they got their first coach and learning one and its systems is like being spoon fed with a shovel.

[DON]

In the area below drivers seat, by windshield washer jug is the pressure switch for the compressor….could have failed or been turned off there..

[Steven]

Steve,

I fixed your signature for you, you can make any change you want by going to the Blue Boxes on the right side of the main forum page and click on “Profile”.

[Steven]

thank you

[Frank]

I started the coach and let the pressure build on idle and the belts never tightened up so it must get it’s air from the aux. compressor. The question is, how do I get air to those belts so I can drive it? I do not see anywhere I can introduce air into the system to do this. I’m just trying to understand in my mind how this works……the aux compressor runs the air bags, the belts, and the toilet, bed,false floor and lock. So the compressor on the engine just operates the brakes. Am I right?

[Archived]

We have Liberty #331, a 1996 XL 40. It’s a 12v Liberty called a “Classic”. The “Classic” has an ole school electrical system. You know, switches, fuses, relays, and CBs that have been around forever(like me) so I know how to work on it. It has almost no curcuit boards, multiplex wiring, or obsolete operating system(s) or software. I have no idea what our Liberty’s have in common. But here is how ours works.

The ignition key has nothing to do with our aux compressor.

The aux compressor is in the front compartment, behind the CruiseAir condensors, and lives in its own wooden enclosure. It can be seen by folding down the frt bumper, or thru the driver side lower steer door. It is 120v. We installed a new quieter aux compressor, California Air Tools MP100. The original was a Gast brand.

So for it to come on we need to have the inverter on that feeds it on. Ours is fed by inverter #2, so we turn on that inverter The switch for the aux compressor is the bottom one on the left row of switches in the electrical cabinet next to the frig.

If yours is like ours, turn on the aux comp switch, and if your house batts are good, your inverter is good, and the aux comp is good, and the aux system is low on pressure, you’ll here the aux compressor run until it reachs its upper set point, at which point it shuts off. I have mine set at about 70 psi. I have mine set to come back on at 50 psi. Obviously, ours has an adjustable pressure switch. Other sources of 120v for the aux comp is the generator or shore power. But no matter where the aux comp gets its juice(120v), the inverter must be on and working. Dead inverter, no aux compressor, or anything else that is on that inverter.

Ours didn’t come with an aux pressure gauge. I added 2 of them. One in the dash, and on in the steer compartment.

Of course the other way to fill up the aux system w/air, is to start the Detroit and let the engine driven compressor fill up the aux system. The red handle valve just inside the engine compartment doors and up high has to be closed(as pictured).

I never start my Detroit with loose belts. I power up the aux compressor and have it build aux system pressure to 20-30 psi, then turn off the aux comp, turn the ignition key to on, then go to the engine compartment and start the engine with the switches that are there. This way I can see if everything is AOK. We ruined a newish fan belt once when I use to start it with the belts loose. Once bitten, twice shy.

I hope this helps. Anyone can contact me privately. I’ll try to help.

[kenneth]

That’s good information Don! I always make sure the belts are tight when I start mine also. My panel looks a little different than yours. My light rocker switches are on top and run across those other switches you were pointing to in the picture. Everything works on that inverter side so I’m assuming that’s ok. Is the compressor located under the drivers seat? I have a door there I can’t open right now. Tried to open it and the lock screwed up and now I can’t get the key out. That is where the clicking is coming from when I turn the switch on the panel on. There doesn’t seem to have any air in the system so I think it’s calling for air. That’s a good idea with the air gage on the dash! Did you get a split gage for the brake air and replace the other gage with one for the aux. compressor?

[George]

On a 98 Liberty it is likely your aux compressor is between the 2 second bays. Maybe. I think.

If you have accessory system pressure and the belts are not tightening it could be the red valve above the engine behind the engine doors.

[Ryan]

Steve,

Yes, all my other buses had a dual needle brake gauge. So I put one in my Liberty and put an aux gauge in the empty hole where the other brake gauge was.