Foretravel Owners' Forum

Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: JBC300 on September 01, 2019, 05:54:20 pm

Title: Air Pressure
Post by: JBC300 on September 01, 2019, 05:54:20 pm
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
Title: Re: Air Pressure
Post by: Super8mm on September 01, 2019, 06:53:03 pm
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
Title: Re: Air Pressure
Post by: DavidS on September 01, 2019, 07:02:48 pm
Possibly bad gauge? Swap one gauge for the other and see if it's the same .. if not that is a start.
Title: Re: Air Pressure
Post by: Chuck & Jeannie on September 01, 2019, 07:51:53 pm
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 (https://www.foreforums.com/index.php?topic=37157)

FRONT PRESSURE GAUGE READING 155 PSI AND RISING (https://www.foreforums.com/index.php?topic=31702)

Air tank differences (https://www.foreforums.com/index.php?topic=28634)
Title: Re: Air Pressure
Post by: pibutler on September 01, 2019, 08:32:19 pm
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 (http://beamalarm.com/Documents/stopping-with-air-brakes.html)
Title: Re: Air Pressure
Post by: Pamela & Mike on September 01, 2019, 08:55:52 pm
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
Title: Re: Air Pressure
Post by: JBC300 on September 04, 2019, 02:21:41 pm
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
Title: Re: Air Pressure
Post by: Old Toolmaker on September 04, 2019, 08:18:46 pm
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!
Title: Re: Air Pressure
Post by: turbojack on September 04, 2019, 08:25:39 pm
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.
Title: Re: Air Pressure
Post by: Tim on September 06, 2019, 04:39:25 am
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.
Title: Re: Air Pressure
Post by: Realmccoy on September 06, 2019, 06:39:25 pm
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.
Title: Re: Air Pressure
Post by: Old Toolmaker on September 06, 2019, 08:22:54 pm


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!