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Air Pressure

On my 01 36', my front pressure gauge started showing low?  I used it last week with no issues. Parked it, and now when I start it, the rear pressure gauge comes right up to 125 psi, but the front gauge shows between 0 and 25 psi and the alarm stays on.
I have pressure for the air bags, horn, and step, but the alarm stays on and the front pressure gauge stays at 0 or may go to 25.
I went under from front to back trying to listen for a leak, but didn't find anything while running and not running.

I'm stumped, any suggestions ?

Thanks to all.
Mark & Bev
2001 U295 36'
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Air Pressure

Reply #1
Are you able to get to ride height? Gauge might be bad?

1 way Valve might be stuck.

Mine has one right off the tank. Looks like a mini gas valve for the bbq

Re: Air Pressure

Reply #2
Yes I can get ride height. I can raise it all the way up, down, etc., front and rear.  Which tank would the 1 way valve be ? I have 2 tanks in front and one in back.  Is it like a solenoid type valve ?
Thanks for the response, I appreciate it.
Mark & Bev
2001 U295 36'
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Air Pressure

Reply #3
I am. It sure where the alarm is tied in.. maybe try swapping the gauges ? Not sure which tank is which under their .. sounds like you have pressure .. just no gauge.

Maybe tap the gauge with a finger

Re: Air Pressure

Reply #4
I am. It sure where the alarm is tied in.. maybe try swapping the gauges ? Not sure which tank is which under their .. sounds like you have pressure .. just no gauge.

Maybe tap the gauge with a finger
I think it's unlikely that the pressure gauge and the pneumatic switch for the warning signal would fail at the same time.

So you have a pair of manual tank drains behind your front bumper?  Opening and closing those should tell you if the tanks for your front and rear brakes have the same amount of air pressure.  Those tanks are separated by an automatic valve for a reason.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Air Pressure

Reply #5
If no pressure to the brakes .. they would not release?

Re: Air Pressure

Reply #6
Post (by Roger) linked below includes a air system diagram for 2001 U320.  Should be the same, or close, to OP's 2001 U295.

Air goes from wet tank directly to front and rear tanks.  There is a check valve at inlet to front and rear tanks.  I think it is highly unlikely that the check valve is blocking air flow into the front tank.  Possible...but VERY unlikely.  Check valves usually fail to the open position.

There is a pressure sender on both front and rear tanks.  They send a signal to the electric air pressure gauges in the dash.  I think there is a good chance that the sender in the front tank is bad, or the wiring from sender to gauge is bad.  I don't know where the low air pressure alarm gets it's signal, but I would not be surprised if it comes from the very same sender.

IF my suppositions are correct, the pressure in the front tank is actually the same as in the rear tank.  The faulty pressure sender in the front tank may be causing the low reading on the front gauge, and the low air pressure alarm.

Air system
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Air Pressure

Reply #7
Found another thread pertaining to the OP's model year coach.  Has more informative posts by Roger.  Apparently on the 2001 model coaches, the signal from the air tank pressure sensors goes to a mysterious "gray box" which then relays the info to the electric dash gauges and to the alarm module.  Erroneous gauge readings can be due to a bad sender, bad gauge, OR a failing "gray box".  Read the thread for more details:

Mechanical Air Pressure Gauges
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Air Pressure

Reply #8
On mine there is something in the gray box that failed.  Apparently it is not repairable or replaceable. The pressure transducer at the tanks and the wiring checked out.  The electronic gauge seemed OK as well.  The unfortunate result of this is something in the box thinks there is no pressure and causes the dinger to ding.  I added a switch to the annunciator to silence it.  I replaced the electronic gauges with direct read mechanical gauges.  I ran air lines directly to the tanks.  I like this much better.  Engine on or off, I see the pressure in the tanks.

My dash volt meter died as well.  I see voltage on VMSpc so that space is now an air pressure gauges for the HWH tank.

In another post I described the method to make the turn signals make the annunciator make noise with the turn signals.

There are three air schematics for the 2001 U30s.  The right one depends on your build number.
I am not sure about the U295 but it is basically the same.

Re: Air Pressure

Reply #9
Thank you very much to all, the information provided here will be very valuable in my quest to find the issue.
Mark & Bev
2001 U295 36'
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Air Pressure

Reply #10
Hi Mark,

Your 2001 problem has some similarities to our 2002 coach. Our buzzer/alarm also wouldn't stop sounding one morning at Grand Canyon. Had to disconnect it. The OEM FT electrical pressure gauges read low one tank and high in the other. We did visual inspections of air bags at every stop to confirm we had travel mode. We also added the DOT brake test to our pre-flight checklist as a safety procedure. Recommend Chucks link:

Apparently on the 2001 model coaches, the signal from the air tank pressure sensors goes to a mysterious "gray box" which then relays the info to the electric dash gauges and to the alarm module.  Erroneous gauge readings can be due to a bad sender, bad gauge, OR a failing "gray box".  Read the thread for more details:
Mechanical Air Pressure Gauges

Also search for this topic on the forum: "Blue Module" failure. Sorry I couldn't figure out how to copy the link here for you.

On our coach I did the following when we got home:
1. Swapped electrical connections at gauges. Result: The pressure readings swapped front to rear.
2. Purchased new pressure senders, installed at front/rear tank. Result: No improvement at the gauges.
3. Installed mechanical press gauges with a tee at each tank so I could keep electrical sensors installed for comparison. The mechanical gauge proved I had proper air in each tank and that fault was somewhere in the electrical gauge circuit. (I suspect the "Blue module")
4. Removed the electrical press sensors and installed a Dwyer Series A2 Pressure NC switch in the tee at each tank. Wired them into a new circuit with a diode for each press switch and a buzzer behind dash. Circuit draws power from ignition switch so it can only sound off when ignition is on. These are adjustable pressure switches. Before installation I set them at 60psi using a small air compressor.

Result: With ignition on buzzer sounds whenever air tanks drop below 60-61 psi.
I have left the FT OEM buzzer disconnected thus far. This means no turn signal chime or HWH audible warning. The turn signal indicator lights and HWH level light on dash still function. We still check air bag travel height in a walk around at every stop.

I would like to get back the turn signal sounds and HWH audible warning. Next project. In the meantime we know what our air pressure is. And the gauges read accurately with engine off. Helps me keep aware of any developing air leaks.

Safe travels, Michael
2002 U270, 36' WTNS, Build # 6030, Cummins 400 ISL.
Wheelchair accessible modifications by ForeTravel, Braun UVL lift.

2001 Dodge IMS RampVan, M&G tow brakes, Sterling tow bar.

Re: Air Pressure

Reply #11
If no pressure to the brakes .. they would not release?
No air pressure, the front brakes can't be set and the rear won't release.  And on my antique GV no throttle. Still not as bad as a 70s Citroen with the big red light shining.

Apropos of nothing, yesterday included a brief lesson on the air cylinder release bolt and the mechanical operation of wedge brakes.  I'm still studying my braking system, where everything is located and how it works.  When I commented that an air brake system is a complicated pneumatic logic network, I got burned from across the table with "Oh, like something you'd design?"
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Air Pressure

Reply #12
Swapped the sending units from the rear to front tank, and then the problem jumped to the rear gauge and showed no pressure.  I now have a new sending unit on order.
A question I have is ...while under the coach following air lines and making sure everything was tight, I noticed what looks to be added on adjustable air regulators with gauges.  One looks to be on the air feed line to the front tank, and then there are two on the front step lines.  Any idea why someone would add these?  They look to be set at about 100 psi.
Mark & Bev
2001 U295 36'
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Air Pressure

Reply #13
Mark,

One is for the step cover piston
One is for the outside step pistons
One is for the air to the front air bags. This is to keep the front from coming up too fast in relation to the rear when you go into travel mode.
They are OEM

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air Pressure

Reply #14
Thanks Mike, were these factory installed ?  Being that they were black plastic adjustable knobs, I assumed they were added. 
Thanks again for the information. I really appreciate it.
Mark & Bev
2001 U295 36'
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Air Pressure

Reply #15
were these factory installed ?  .

Yes they were put on at the factory during assembly.
They are hid down there to keep some owners from constantly tinkering with them.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air Pressure

Reply #16
Mike, Thank you for the info. I am learning.........
By chance, do you know what they should be set at ?
Thanks again,  Mark
Mark & Bev
2001 U295 36'
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Air Pressure

Reply #17
By chance, do you know what they should be set at ?

Mark,
The last time I replaced mine the step cover and step regulators are set at #60.
This can vary with different coaches and how the Noreg shuttle valves are set up.
The one that feeds the air bags is set at #45 IIRC I need to go look this up in my notes tomorrow.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air Pressure

Reply #18
Thank you very much.  Not sure what I'd do without this Forum and people like you.
Mark & Bev
2001 U295 36'
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Air Pressure

Reply #19
My steps shuts at 60 psi.. when key is on and I am waiting to build pressure

Re: Air Pressure

Reply #20
 Mark,

Just looked up the pressure for my front air suspension regulator and it is set at #45.  I went back and changed the previous post to keep from causing more confusion.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air Pressure

Reply #21
Thanks again Mike !
Mark & Bev
2001 U295 36'
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Air Pressure

Reply #22
Any suggestion on brand to use and is it 1/4 npt?

2000 GV320 4010 build #5712  2019-?
1999 Bounder 2000-2008
Bardstown, KY
🥃The Bourbon Capital of the World🥃

Re: Air Pressure

Reply #23
Any suggestion on brand to use and is it 1/4 npt?

This is what we put in our FT when we had it.  That was after 2 failed (one right out of the box) pricey ones from FOT

Air leak up front -- need your advice
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

Lifetime Escapees' member SKP 82766
Former 1999 30IB Lazy Daze (2000-2004)
Former 2003 U320 (2004-2016)
Former 2017 LTV Unity (2017-2023)
Shopping for our next coach

Re: Air Pressure

Reply #24
Michelle,

Amazing how you guys can find this info so fast, I can look at threads all day and not find what I am looking for.

Thanks again!
Tommy

2000 GV320 4010 build #5712  2019-?
1999 Bounder 2000-2008
Bardstown, KY
🥃The Bourbon Capital of the World🥃