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Orange dial on air pressure gauge issues

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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

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