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Topic: Air Pressure (Read 871 times) previous topic - next topic

Air Pressure

First let me introduce myself.  The name is John and better half is Linda.  We live in Northeast Texas about 2 hours north of MOT and this is our third Motorhome.  The motorhome is a, new to us 1998 Foretravel U-270 that we have owned about 6 months.  I am a great believer in forums and we have found a lot of solutions to problems by reading them. 

My problem today is the front, top gauge, air pressure.  When we bought the motorhome the top gauge ran a littler higher, about 125 pounds, than the bottom one.  During a trip to Utah it started going up a little at a time each driving day, and the last day of the trip it ran all the way on the peg.  The bottom gauge runs 90 ti 120 pounds.  What really blows my mind is that it took three weeks of driving to go from 125 pounds to completely peg out the gauge. 

Anyone have any ideas?

John

Re: Air Pressure

Reply #1 –
Welcome. I am sure other will come along and help you out.  I think there is a regulators on the tanks?

Others will know for sure
Steve

1997 U270 36' build 5179
Motorcade #18147
1980 CJ5

Re: Air Pressure

Reply #2 –
Possibly bad gauge? Swap one gauge for the other and see if it's the same .. if not that is a start.

Re: Air Pressure

Reply #3 –
Welcome to the Forum, John & Linda.  You have come to the right place to learn about your coach.  Lots of accumulated knowledge here.

99% probability it is a false reading on the "high" gauge.  The way the air system works on these coaches, it is impossible for one single air tank to greatly exceed the normal operating pressure range, which as you have noted is usually around 90-120 psi.

So, you need to figure out why the "high" gauge is reading falsely.  Is it a mechanical gauge, or electronic?  Mechanical gauge will have a air hose attached to the back of the housing.  Electronic gauge will have only electric wiring.

If mechanical, you can swap the air lines between the two gauges.  If the "bad" gauge still reads high, then you will need to buy a new one.

If electronic, you might be able to switch the wiring somehow between gauges, and see if the false reading moves to the other gauge.  I don't know how difficult that would be, cuz I have mechanical gauges.  Another member might be able to tell you.  Electronic gauges are a bit more complicated, because they require a remote sender unit that supplies the pressure signal to the gauge.

Do you have a air system diagram for your coach?  Working with/on the air system is much easier if you have a diagram.

The threads linked below will give you an idea of how we suggest trouble shooting bad air pressure gauges:

Air Pressure

FRONT PRESSURE GAUGE READING 155 PSI AND RISING

Air tank differences
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
"Surely, no age has been more fraught with insecurity than our own present time."

Re: Air Pressure

Reply #4 –
The air brake system should have a relief valve that protects the system - I think 150psi is the top end. If you were over pressurizing your system it should bleed off and you would hear it - and it not the "swoosh" sound you hear when the brakes "spit" or "purge" through the dryer.

Here is a video from one of the forum members that explains the brake system - just good stuff know.

air-brakes-how-they-work

Re: Air Pressure

Reply #5 –
A '98 270 should have mechanical gages, not the electronic ones with the magic box.  My vote is a bad gage. With it gaining a little every day that sounds like the needle has came loose from the post.

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 #6 –
Thanks everyone I am going to see what type of gauge I have and try the swap. 

Thanks i have a lot to lean about this coach but i do love it.

John

Re: Air Pressure

Reply #7 –
Quote from: JBC300 –
Thanks everyone I am going to see what type of gauge I have and try the swap. 

Thanks i have a lot to lean about this coach but i do love it.

John

I don't need a hobby.  I own an RV!
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 #8 –
When you get time you need to put your coach information in  your tag line.  That way everyone know what coach you have  without you having to tell everyone every time.

Button on top right that says My Account and then Forum Profile I believe gets you there.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Air Pressure

Reply #9 –
Same here. Replace your gauge.

Or, if you are handy, so you can disassemble it and reattach the needle with a drop of crazy glue. The needles sometimes get loose due to vibration.
1997 U270 34FT Build 5140 Cummins 8.3 Allison 3060R
Solar 1920Watts, 14KWH lithium. Orion BMS.

Re: Air Pressure

Reply #10 –
I also have 98 U270 and live in McKinney. Can't help with this but have worked through a few issues in last three years. My first diesel pusher, huge learning  curve. We ought to talk. I'll be in Tyler Sept. 27/28 if plans work out.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.
 

Re: Air Pressure

Reply #11 –
Quote from: JBC300 –


My problem today is the front, top gauge, air pressure.  When we bought the motorhome the top gauge ran a littler higher, about 125 pounds, than the bottom one.  During a trip to Utah it started going up a little at a time each driving day, and the last day of the trip it ran all the way on the peg.  The bottom gauge runs 90 ti 120 pounds.  What really blows my mind is that it took three weeks of driving to go from 125 pounds to completely peg out the gauge. 

Anyone have any ideas?

John



I have spent the three months of Foretravel ownership reading manuals and researching systems.  I'm a retired toolmaker and once upon a time that was a big deal, that being said I enjoy understanding how everything works while it's still working as it should.  A luxury I wasn't usually afforded on the job.

Yes there's a small auxiliary air compressor for you leveling system when the main engine is off but all of your air pressure comes from the engine driven compressor so one gauge can't peg itself.

After 6 years of living with questionable hydraulic brakes I love having brakes that need to be feathered during slow speed maneuvering!
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.