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Topic: How to use my air tank switch (Read 1204 times) previous topic - next topic

How to use my air tank switch

I was reading another current topic Leaning Coach, Air Check Valves and it made me realize I really don't know what my air tank switch actually does and how it can be used.  All my manual says is "Controls auxiliary air compressor for coach air system.  May be used to fill coach air system when engine is not running".

So, Why would I want to manually fill the air system?  How long can the pump run?  If I turn on the pump will it shut off automatically? 

Any additional info would be appreciated.
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Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit

Re: How to use my air tank switch

Reply #1 –
I would like to know more about the air systems myself and plan to remove, dismantle, clean and reinstall all air valves.

Mark mentioned an "air tank switch" and I do not know if I have one of those.

The 12 volt air compressor in my 1996 U320 will run when the HWH air control panel is set to auto-level, the coach is not level, and the engine is off. This air compressor provides air to the air bags but does not air up the tanks which contain air pressure for the brakes. The HWH system turns the air compressor on/off as needed to keep the coach level.

I added a switch at the air compressor so I can turn this compressor on with the cargo door open. It will run until maximum set pressure is reached (120psi) in air bags, at which time the coach will be raised to maximum air bag height. This compressor did not build pressure when I purchased my coach because the water seperator bottom fitting was cracked. After I replaced the cracked fitting, it would not shut off at max pressure because the pressure switch was clogged. I dismantled and cleaned everything and it works fine now. I installed a quick connect plus a pressure gauge between the compressor outlet and the air line leading to the air bags. I can now disconnect the air bag line (check valve keeps air pressure in air bags) and connect a tire fill hose to top up tires.

There is an air line with a manual valve and a quick connect beside the fuel tank on the passenger side. This has little value because it provides air from the brake air tank which  has between 90psi and 115psi only when the engine is running. This air line can be used to fill car tires but has insufficient pressure to fill motorhome tires. 
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: How to use my air tank switch

Reply #2 –
Wyatt,

We do not have the "air tank switch" on our coach. The air system on our '97 U295 is like the system on your 1996. Our manual includes drawing B-2036, "U280/U295C E21 AIR SCHEMATIC." I infer from descriptions in this thread that the switch would bypass check valves that isolate the 12VDC compressor from the brake system.

Pressure from the 12VDC compressor provides pressure for the leveling system, but does not pressurize the brake system. The pressure gauges on the dash normally approach zero if the engine has been off for a couple of days. The leveling system will usually hold pressure for weeks without running the 12VDC compressor.

I have cleaned the purge valve on the 12VDC compressor water separator a couple of times. Debris has accumulated add kept the valve from closing properly.

I do use the air from the brake system via the quick connect near the fuel tank. Tires need only be inflated to 90 psi in order to exceed requirements for the weights on our axles.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: How to use my air tank switch

Reply #3 –
Quote from: Mark Benko –
I was reading another current topic Leaning Coach, Air Check Valves and it made me realize I really don't know what my air tank switch actually does and how it can be used.  All my manual says is "Controls auxiliary air compressor for coach air system.  May be used to fill coach air system when engine is not running".

So, Why would I want to manually fill the air system? 

Mark,

Our primary use of the Air Tank switch is to start filling the A and B tanks before we're going to drive somewhere.  We use this as a courtesy to other campers since it allows us to keep coach engine running to a minimum before being able to reach full pressure, travel height and driving off.

There is a pressure switch with upper (off) and lower (on) limits for that pump.  I recall upper is somewhere in the 75-95 psi range and the aux compressor will pump until it reaches that upper limit.  That could take 15 minutes or more if the tanks are low and worse if you have a leak, so I wouldn't recommend leaving the switch on without being present.

Michelle
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: How to use my air tank switch

Reply #4 –
Quote from: Michelle –
Mark,

Our primary use of the Air Tank switch is to start filling the A and B tanks before we're going to drive somewhere.  We use this as a courtesy to other campers since it allows us to keep coach engine running to a minimum before being able to reach travel height and driving off.

There is a pressure switch with upper (off) and lower (on) limits for that pump.  I recall upper is somewhere in the 75-95 psi range and the aux compressor will pump until it reaches that upper limit.  That could take 15 minutes or more if the tanks are low and worse if you have a leak, so I wouldn't recommend leaving the switch on without being present.

Michelle
Rick & Colleen
2003 U320 38'

Re: How to use my air tank switch

Reply #5 –
Oops sorry about the last post.  Michelle, are the A and B tanks you are talking about the primary and secondary tanks used for the air brakes?  I thought those were only pressurized by the compressor attatched to the engine, hence having to run the engine to recharge.
Rick & Colleen
2003 U320 38'

Re: How to use my air tank switch

Reply #6 –
Quote from: Rick & Colleen –
Oops sorry about the last post.  Michelle, are the A and B tanks you are talking about the primary and secondary tanks used for the air brakes?  I thought those were only pressurized by the compressor attatched to the engine, hence having to run the engine to recharge.
The A&B are the brake air tanks, normally and primarily taken care of by the engine compressor. 

When you flip the "air tank" switch on the console, it opens/closes a solenoid located in the HWH compartment.  The solenoid is near the HWH pump output / pressure switch and looks very much like the other air solenoids located on the leveling manifolds under the coach.

On ours it opens / connects air line 76 to the pump.  This air line (76) then goes to the "wet tank" and from there it pressurizes the air brake tanks.  So when that switch is on, the 3 tanks (ok 4 with wet tank) are all linked together and the HWH pump will bring them up to 95psi (or whatever your HWH cutoff is set to) assuming of course the pressure is low enough to call for the HWH compressor to start (normally below 65-75 psi).

Normally the HWH pump is only hooked to line 75, thats the slide out air tank, and line 57, which feeds the leveling manifolds.  So when the coach needs air to level the HWH pump sends air out line 57, to the leveling manifolds and then on to the appropriate air bag that needs inflating.  It also comes on to maintain the pressure in the slide out air tank to keep the slide bladders inflated (line 75).

Note those are the line numbers are what are in our coach, the numbers may be different in your coach, check your air schematic if you have one.
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"

Re: How to use my air tank switch

Reply #7 –
Thanks Steve.  Excellent explanation as usual.
Rick & Colleen
2003 U320 38'

Re: How to use my air tank switch

Reply #8 –
Thanks Michelle and Steve.  You folks are really considerate of your fellow campers!  Our coach "airs up" in less than 5 minutes after starting so I'm not sure how much time I can shave off that.  but hey, I'll test it out!

So, theoretically, I could also use the aux pump to top off my tires which only need 95/85 psi?
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Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit

Re: How to use my air tank switch

Reply #9 –
I do not have that switch I think.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: How to use my air tank switch

Reply #10 –
John, think I said in my thread that got into this matter, I do not have such a switch either in my 2001.  It sounds very good to have but no one has suggested I can add those solenoids.

I very much appreciate Steve's summary.  I was told by MOT staff that the valve at my line 57 was one problem in my coach.

I read, some might be able to use the auxiliary pump to pressurize the system and then air the tires?  In my case, I am much better off to crank the engine for that, I need 110 psi in tires.

I had the same crack in the water separator fitting as Wyatt described, so hearing that he had it too might be good to check that if your aux compressor runs more than it should.

Duane told me his pump never runs.  His wife said yes dear it does, you just to not hear it!
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches
 

Re: How to use my air tank switch

Reply #11 –
Quote from: Steve –
The A&B are the brake air tanks, normally and primarily taken care of by the engine compressor. 

When you flip the "air tank" switch on the console, it opens/closes a solenoid located in the HWH compartment.  The solenoid is near the HWH pump output / pressure switch and looks very much like the other air solenoids located on the leveling manifolds under the coach.

On ours it opens / connects air line 76 to the pump.  This air line (76) then goes to the "wet tank" and from there it pressurizes the air brake tanks.  So when that switch is on, the 3 tanks (ok 4 with wet tank) are all linked together and the HWH pump will bring them up to 95psi (or whatever your HWH cutoff is set to) assuming of course the pressure is low enough to call for the HWH compressor to start (normally below 65-75 psi).

Here is a the electrical diagram showing that circuit.
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"