[Richard]

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.