09-11-2017, 07:13 AM
Thanks Bill. It sounds to me as if your travel valves might be remaining open all the time or much of the time despite the settings on the control panel. If the HCVs are at travel height they are closed and would lock the current air pressure in the air bags even if the travel solenoids are open. If they are below the set height they will try to add air from the SUPPLY air pressure, if that air pressure is below that needed to raise the coach then the air bag pressure will flow backwards through the HCVs to the SUPPLY tank, this will only happen if the TRAVEL solenoid valves are open.
My thoughts are to do a couple things. First, do not replace the HCVs unless they are proven to be a problem until after this "dropping" problem is solved. Changing parts can cause new problems to arise which will just complicate finding the current problem.
Second, use Richard's famous solenoid valve test to check if they are energized by placing a screwdriver tip on the center post of each and see if you detect the pull of magnetism. Do this in first in the travel mode to see what it feels like and then after dumping or any setting you have used in this testing process other than TRAVEL. While you are at it, also check all the other solenoids to see if they are acting according to what you would expect. This test will verify whether the electronic control brain is working correctly.
If nothing shows up in the electrical test, then I would pull the lines coming from the HCVs to the travel solenoids to see if air is flowing out of those solenoids toward the HCVs. Do this test in any mode other than TRAVEL. This will test the mechanical integrity of the travel valves.
What I find strange about your situation is that the whole of the back drops together. Given that this problem started suddenly and has been consistent leads me toward a single component failure causing the symptoms you are experiencing. So, we are searching for a single component failure that can cause both sides to drop at a similar rate. The only single component that I can think of that could effect both sides is the electronic controller for the leveling. The odds that both travel valves or both HCVs would fail exactly simultaneously seems incredibly small.
I hope this is helpful to you
My thoughts are to do a couple things. First, do not replace the HCVs unless they are proven to be a problem until after this "dropping" problem is solved. Changing parts can cause new problems to arise which will just complicate finding the current problem.
Second, use Richard's famous solenoid valve test to check if they are energized by placing a screwdriver tip on the center post of each and see if you detect the pull of magnetism. Do this in first in the travel mode to see what it feels like and then after dumping or any setting you have used in this testing process other than TRAVEL. While you are at it, also check all the other solenoids to see if they are acting according to what you would expect. This test will verify whether the electronic control brain is working correctly.
If nothing shows up in the electrical test, then I would pull the lines coming from the HCVs to the travel solenoids to see if air is flowing out of those solenoids toward the HCVs. Do this test in any mode other than TRAVEL. This will test the mechanical integrity of the travel valves.
What I find strange about your situation is that the whole of the back drops together. Given that this problem started suddenly and has been consistent leads me toward a single component failure causing the symptoms you are experiencing. So, we are searching for a single component failure that can cause both sides to drop at a similar rate. The only single component that I can think of that could effect both sides is the electronic controller for the leveling. The odds that both travel valves or both HCVs would fail exactly simultaneously seems incredibly small.
I hope this is helpful to you
Jon Kabbe
1993 coach 337 with Civic towed