[jee7s]

The inoperable pressure switch could be explained by wiring. Last year, we found the switch needs to be pulled up with a resistor (100K or so) in order to give a proper signal. This way, the controller sees 5V when the switch is open, and ground when it is closed.

Without the pullup, you get ground and high Z (read "floating")..which is an indeterminate state. The controller won't see a state change no matter what you do...so the tanks over charge. (NB: The switch doesn't turn off at exactly 120psi, but usually a little bit more.)

-JEE