gaggia espresso machine - how it works

 wiring diagram:

machine powered on, boiler heating up:

water heated up( at 105 C) , brew switch ON:

 

 

steam switch ON:

brew thermostat is by-passed. boiler continues to heat up when boiler is below 145 degrees C, and steam thermostat is still closed. When boiler temperature reaches 145 degrees C, steam thermostat is open, and boiler stop heating

both brew and steam button ON:

this is a single boiler machine, and is not supposed to brew and steam at the same time. Anyways, 3 way solenoid valve is switched off, but pump is still running, no water comes out from group head, no water coming out to drip tray. the water is flowing from OPV back to water reservoir instead

physics of a coffee maker