Disconnecting the pressure switch is not taking it apart mate, its just not connecting them 2 wires to it, just the ones off the pump.
Sounds like you could do with setting up the varistream. Turn it on, un couple the hose so the pressure can build, press and hold the + & - buttons and the display will change, again press and hold the + & - buttons and it will flash, have a little play until it turns off, you have from a, b, c, d, e, f, and 1 - 10 i think.
Its just a setting to work out what pressure to turn off at as we all use different hoses connection etc, hope this help mate.