Recently we had a similar problem. We had a solenoid (coil) burned out on the dump valve. Replaced the valve ($245). No joy. The valve really was bad, but there was another problem. The HWH touch control pad is bad. It sends a constant signal to the dump coil. This means that when I start the engine and let the system actuate the air bags, the dump valve will not let it work. It took me a whole week to diagnose the problem.
I finally unplugged the electrical cable to the dump solenoid. That allows the airbags to inflate properly. I can't dump the bags, but I don't care enough to buy a new $450 touch control pad to replace it.
My chassis is Spartan, so your controls may be different. Mine has a 3-way Parker air valve with two solenoids. When the engine starts and the tranny is engaged, the "ride" side solenoid kicks on. I don't know if it stays under power or just kicks on for a moment. I do know that once it is actuated, it stays that way until the other coil kicks it back. The valve also has a little manual override button that works even when there is no electrical power to the valve. You can shift it where you want it and it will stay until the coil kicks it back. Unplugging the cable leaves it where you left it. Mine is now set to ride. I'll fix it right later.
If you need any more cheap advise, don't hesitate to ask.
Tom & Jan ---- Westwing43
2005 NEWMAR KSDP 3910 NOW PULLING A 2014 CHEVY CAPTIVA