Orange dial on air pressure gauge issues

[Bob Disney]

I have an intermittent issue that appears to be getting worse.
The orange needle on my air pressure dial occasionally starts to drop and causes the alarm to go off.
I have not been able to find air leak anywhere.
My cruise control quit working as well
My brake light worked just fine.
The green needle seems unaffected
I hit a bump yesterday while the alarm was going off the alarm stopped suddenly and the orange jumped back over to 120 pounds.
I believe I still have plenty of air in the tank.
Two days ago Dave Atherton did a ECM diagnostic it showed brake sensor issues
I’ve been through the coach and can’t find my air tanks, but will continue to look.
It appears there’s two brake line sensors, and I can only find the one attached to the firewall next to the brake foot  valve
This is a 2005 beaver Monterey Ventura IV.
If anybody else has experienced this, I should really like to hear from them.
I’ve had tons of speculation, but nobody really knew
I imagine it’s probably a faulty sensor, but I can’t even find that

[Bob Disney]

I finally found my air tanks.
I have a slide drawer in the same bay as my inverter.
I pulled everything out of my slide drawer and slid in on my drawer and found my air tanks.
Now I have to find a electrical connection to them somewhere

[Bob Disney]

As it turns out while I found a pressure sending unit I was feeling around I could feel a slight air flow
The pop off valve on one of the tanks was loosing air
After a trip to NAPA to get line wrenches (regular wrenches were stripping the flats on the brass)
I was able to remove and replace the high pressure relief valve
Will see if that fixes the problem

[Bob Disney]

That didn't fix the air leak
I believe now that we have a bad unloader valve on the compressor
I have one ordered and hope to have it on today or tomorrow/ I purchased a Bendix as that is the compressor brand used on our coach. OEM is always best
I also replaced the hose from the governor to the valve at the compressor as a precaution, the old one showed some wear on the SS braiding
The leaky pop off valve replacement slowed down the air from escaping overnight but not the pressure drop while running down the road.
I have been fighting this for a couple of years and have had it in the shop a couple of times
It appears that this is not at all a uncommon of a problem,
I'm home for a extended time now and will not know if replacing the valve will fix it, until we take another trip

[Eric Maclean]

Bob
It appears that your on the right track , if the problem is while driving the air governor controls both the unloader valve in the compressor and the purge valve in the air dryer.
The braided air line you referred to is the air discharge line from the compressor to the air dryer the air passes through the air dryer and exits through a check valve in the dryer before running via a air line ( usually green ) to the wet tank.
If the check that  valve goes bad or sticks the air can leak backwards through the air dryer when the compressor is not pumping
To check that check valve disconnect the braided air line with air in the tanks and engine shut down and check for air leaking from the dryer connection.
When you replaced the old braided discharge line was there signs of excess oil passing from the compressor?

With all the work you've done now might be a good time to clean and service the air dryer .
The links below should help you to understand the operation of the governor, unloader and dryer operation .
Your coach most likely does not have a Bendix  air dryer but the operation will be the same .


https://youtu.be/bmgSwSeLk_o?si=Cr926sIOiIVIZv5F


https://youtu.be/7phjlysl7Zo?si=9kMvxbicFKKgDI5t

Hope this helps
Eric

[Bob Disney]

Relaced the air dryer a year ago
May replace the filter, probably have 15,000 miles on it
Also ordered replacement purge valves for the tanks all 4 should be here tomorrow
I've never seen any leaks there until I soaped them today, extremely slow leaks from all four of them

[Eric Maclean]

Bob
At 15000 miles on the desiccant pack I wouldn't bother .
Depending on the weather conditions the coach is driven in the service interval can very dramatically for example if you were in a very cool and high humidity area like the east coast or Oregon where there is very humid conditions the desiccant will have a shorter life than in a very dry area like Arizona.
Take into account thr dryer purges the desiccant chamber with each cycle of the air compressor, so if you have a lot of air leaks creating more air demand on the compressor the resulting extra air flow with also shorten desiccant life.
But for the most part with motorhomes the average usage isn't in rainy wet air and with limited miles each year the desiccant package should be good for about 5 years of normal use and probably more .heck I've seen 20 year old coaches running the factory installed desiccant filters and still working fine not that id recommend that.
The tell tale of a bad desiccant filter is excess water buildup in the tanks.
The danger of leaving a desiccant pack too long is that the desiccant will eventually plug up and bust it's container with in the filter which allows the many small beads of desiccant to travel into the air system creating problems with valves and components (a bad thing ).

Hope this helps
Eric

[Eric Maclean]

Bob
If your still chasing leaks check your exhaust brake air solenoid ( if you have one ) for a small leak through its exhaust port .
Also check the brake treadle valve at the floor for leaks around the roller spool as the tend to collect dirt and create small constant leaks there as well.
And while your there lube the pedal higher to make sure the pedal moves freely and does not stick.

[Bob Disney]

I've been thinking about that valve and brake light switch
Just bubble tested the valve a month ago
The coach still looses air overnight, its leaking somewhere

[Eric Maclean]

Bob in my tool box I have several  sizes of pipe plugs to help track down leaks .
Using the pipe plugs I can disconnect air lines from the air tanks and plug the air tank port to narrow down my search to one air circuit at a time .
Some leaks are almost impossible to detect but if your going down over night it should be easier.
To find those smaller leaks I use a product for refrigeration called Big Blue micro leak detector.


https://www.amazon.com/Refrigeration-Technology-REFRIGERATION-TECHNOLOGIES-RT100G/dp/B0058E0Q0M/ref=asc_df_B0058E0Q0M/?tag=hyprod-20&linkCode=df0&hvadid=509398599309&hvpos=&hvnetw=g&hvrand=9600109843375773313&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9011305&hvtargid=pla-928527643191&psc=1&mcid=9a16e26447cf33e7b6d30ef21be3bd2f&gclid=Cj0KCQjwhtWvBhD9ARIsAOP0GojG5xJmGB0Wa-UgRYjqirZNKS-RvUEUqIkgzMy5_QBKaeRV8HjCrBgaAk28EALw_wcB

[Bob Disney]

Sounds good Doesn't seem to leak down so bad if I'm using the air level
Hmm... maybe the leak is in the 12 volt compressor system
How much would you use and
How do you introduce it into the system?

[Eric Maclean]

The air leveling compressor usually uses a separate tank and has a check valve between it and the coach air supply so the little compressor doesn't have to try and keep the chassis air tanks topped up it only maintains the small tank for air leveling purposes.
You should be able to drain all the chassis air tanks and wait for several hours or days to see that the check valve holds air on the small air tank,
This will mean getting to that small tank to open the drain ( which is a good idea anyway as most never get drained)
That small tank should hold air and of course the small compressor is there to keep it topped up so that when the chassis air is depleted the leveling system can still maintain level.

But of course you could use the pipe plugs to eliminate the whole circuit temporarily  to be sure.
I usually start with the accessories feed lines ( suspension, HVAC, horns )at the tanks do one line at a time pressurize the tanks and wait to see if it makes a difference if not leave that one plugged and move on to another line until you have found the culprit.
Once you've found the effected circuit then you can check each connection and component on the circuit until you find you leak.
Start by checking the ride height control valves as they move constantly and tend to develop small leaks over time.
Also check all the push to connect air fitting as they tend to leak .
Most coaches have a multitude of small leaks and ( you know death by a thousand cuts).
The question is how far do you want to go to cure them.

Good luck and have fun
Life's to short not to
Eric

[Steve Huber Co-Admin]

Bob,
See  https://beaveramb.org/forum/index.php/topic,12082.msg80225.html#msg80225 for info on leveling compressor. Yours may be located on the pass side forward of the he front wheel, accessible when the  geni slide is out.
Steve

[Bob Disney]

I've drained the leveling tank a couple of times, but probably since late last summer when I was at HWH for service
Next time I get the coach out I'll run it up on ramps and dump the air then soap it good
Cant hurt to check that system