[jcus]

At the risk of another goof on my part on this thread, on the Newell setups I have had my hands on, there is both a well pump pressure switch with high and low setpoints, a regulator, and a check valve to keep the 12V from pressuring the entire air system.

If the pressure is low, it could be a simple adjustment on the regulator. Or it could be the setpoints on the on off well pump switch need adjustment.

I might have messed up, but my air door only worked off eng or ac compressor system. Found a blanked off air line in compartment behind 12 v compressor. So 'teed" it into 12 volt comp discharge and adjusted it  to 60 psi. Whole system stays around 60 psi now, even with no ac air compressor. Do not know if there are any check valves to prevent main system from dumping into toilet, air door, or door slide system in case of leak there, but brake side stays at 120, so know there is a check valve working there.