Bezzera BZ02S - Won't heat up, fluctuating steam pressure for a week.

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

#1: Post by LeveragedBeanJuice »


About a week or so ago I took my BZ02S home to clean it, and fix a steam leak. After I finished, it had issues with maintaining a steady pressure. It would heat up the boiler, and let it go to ~1.3, and then let it drop down to .5, then back up, down, up down. I figured it was just some fluke that would sort itself out.

This weekend, I took it home again to add a PWM to it, and got some really good shots. After a shot today, it stopped heating the boiler. I can't get it to turn the boiler on at all now.

-I have tried resetting the pstat on the bottom of the boiler, checked the wiring, removed the PWM, etc.
-If I hit the brew button, it will pump water through the boiler and out the grouphead.

As I'm writing this out, I'm getting the feeling it's the Pstat, but I tried resetting it and it and the button wouldn't click so I'm lost.

User avatar
Team HB

#2: Post by Jeff »

What was involved in "cleaning" it? Is there a chance that scale got dislodged and either clogged the pipe to the pressurestat or the internals of it?

I'm not sure what a "PWM" is in this context.

The parts diagrams suggest that it has a mechanical relay. Is there any discoloration on the internal contacts, case, or connectors?

LeveragedBeanJuice (original poster)

#3: Post by LeveragedBeanJuice (original poster) »

I didn't clean the inside of the boiler, probably should at this point. So I don't think that anything got dislodge into the pressurestat.

The steam leak was a crack on the "steam tap hose" (pipe going from boiler to steam valve) that I stopped with silicon tape.

Cleaning involved removing some of the corrosion off the boiler caused by the steam, sweeping out dirt and dust that was on floor of frame (this involved unplugging some wires and plugging them back in), removing the bottom case and cleaning out all of the dirt/corrosion that was in there. I did remove wires from the pressure stat to clean down there, but plugged them right back in. A lot of those connectors do have corrosion, after looking at it a bit ago. Everything worked after all of this though, aside from the pressure fluctuations.

For the record, this is a machine I got for free about a year ago that I spent ~$50 in parts to fix, which is why it was so dirty. It just had a bad brew button. The previous owner didn't realize there was a steam leak which caused all of the corrosion. I'd love to tear it down and clean it thoroughly, but I have too many other projects on my plate at the moment.

A PWM is a basically a dimmer switch that you can use to change the pump pressure. I've seen others add them to their machines and wanted it for mine so it stopped blasting my pucks with 9bar off the bat. It greatly increased the quality of the 10 shots it made till it took a poop.

User avatar
Team HB

#4: Post by Jeff »

The heater circuit is generally simple in these machines. The order varies by maker and model, but generally there is in series a safety thermostat ("Klixon"), a relay, and the element. Often there is a pilot light in parallel with the element that indicates heating. The relay is usually driven by power running through the presurestat. Some machines don't use a relay and run full current through the pressurestat. That is ok on 230 V but the double current on 120 V often causes the pressurestat switch to fail.

LeveragedBeanJuice (original poster)

#5: Post by LeveragedBeanJuice (original poster) »

Yeah, the green pilot light does not turn on right now.

If I connect the wires on the pressure stat, and the pilot light and boiler turn on, would that prove that the pressure stat is bad?

LeveragedBeanJuice (original poster)

#6: Post by LeveragedBeanJuice (original poster) »

If I go ahead and remove the circled terminals from the p-stat, and put them on the circled post, would that bypass the p-stat to see if the boiler and pilot light will turn on? Also, yes, this needs cleaned very badly.

LeveragedBeanJuice (original poster)

#7: Post by LeveragedBeanJuice (original poster) »

Update: I bypassed the p stat and now the boiler will turn on, and pressurize. I'll order a new pstat today.