Bezzera BZ07 Limit Switch trips after adjusting boiler pressure

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

Postby Koen » Oct 12, 2017, 7:46 am

Dear home-barista's! After almost a year of "sneaking" I finally registered to this forum, because I desperately need your help. Two months ago I bought a second hand Bezzera BZ07 (non-PID) with a matching grinder. Nothing seemed wrong with it, looked kinda new to me. Of course, I couldn't make decent espresso's straight away. So as any beginner I started with many, many trial and error, buying a calibrated tamper, La Marzocco VST filters and when I still couldn't get a decent tasting espresso I ended up buying a brand new grinder (Baratza Sette 270). However, after trying multiple freshly roasted beans, my shots still tasted sour. So I thought, if it is not the grind/beans, it must be the water temperature right? Whether or not this assumption is right here comes the real problem:

The problem
I decided to increase the boiler pressure on my machine. The factory setting was 1,2 bar, in little steps I adjusted the pressurestat with a flat head screwdriver till it reached 1,4 bar. I switched off the machine, put the body back on and switched it on again to make a test shot. However, before I was able to make this shot, the pressure dropped slowly but steady back to 0 bar and the water in the boiler won't heat up any more (so no water/steam coming out of the crane/steam tip)... which part have I broken? Please help!


Postby Sander1981 » Oct 12, 2017, 1:01 pm


I don't own a Bezzera but I have a hard time coming up with a reason why increasing the boiler pressure could lead to the machine not working anymore. You could measure whether the heating element receives 230V. If so, it might be broken if the water doesn't heat. If not, then it could be a lot of reasons. The pressurestat could be broken, the electronics could be (I don't know how complex they are, my vintage E61 only has switches), the sensor of the water level, etc. etc. If I were you, I'd start with a voltage meter.



Postby Koen » Oct 13, 2017, 4:59 am

Hi Sander!

Thanks for the cleaver thinking. Armed with your advice and a Voltage meter I put the machine on its side, and removed the lower casing to start measuring. However, I found more than just a + and a - pole, there was a so called " Limit Switch " with a inviting red button reading " press " on it (marked with a green circle in the picture underneath).


So, after googling, I pressed it... and...

The problem turned out to be this " Limit Switch " underneath the boiler :D

I didn't know my machine had one, but apparently it has one and it turned out to be tripped because of the higher boiler pressure. After pressing the button, the machine water in the boiler heated again after turning on the machine. Apparently the boiler itself can handle 2,5 bar, the pressostat 1,5 bar, but this limit switch can't handle 1,4 bar. Any explanations?


Postby Sander1981 » Oct 13, 2017, 12:40 pm

I does make sense if the pressostat can only handle pressures of up to 1.5 bar to set it just below that. The switch can be used over and over again, but if the pressostat would break down you would have to replace it. Great news that it could be resolved without much work or buying replacement parts!