Put a pressure test gauge somewhere on the machine, steam wand works as well as anywhere and bypass the pstat with a wire pigtail....short wire with spade terminals. The pressure gauge is for safety and to basically reduce the nervous factor while you wonder if the safety pressure valve actually works......if it's the pstat a new mater isn't that expensive depending on where you get it. We had a Giotto for a long while and it ate pstats and only now am I getting curious about just what is sealed inside the body of that thing....the microswitch seems to keep on ticking but makes me wonder about the diaphragm inside and just why they "go bad". By the way, if the pstat is bad don't throw it away, the microswitch can still be used.