Greetings dear Barista.

I'm a happy owner of a mk1 Isomac Tea espresso machine on 5th year.
However I recently had to replace the pressurestat, which made the machine run again.
But now after only two weeks of use I heard a sizziling (not the boiler) and suddenly it smelled burned (electronic). I turned the machine off and could see a drop of water laying ontop of a cable plugged into the pressurestat. Waited until it was dry and turned it on again. No problems. But then it went bad again with sizziling and smell which have now resulted in both lights being on all the time - Red and blue displaying if the boiler is on or not. And it doesn't stop at 1.5 bars pressure but continue until I turn off the machine. Is it really dead, or have you heard this case before and can tell me how to fix it?

Best regards from a sad Sebastian

It sounds like you have a water leak somewhere- and in turn has migrated into some of your electronics. A pressure stat opens and closes contacts based on boiler pressure. Both lights on (ruling out shorted or open wiring) would lead to pstat failure,a controller module failure, etc. Do both lights stay on with pressure stat disconnected? (removing power, disconnect pstat and reapplying power).

Sounds dead. Any sizzling and burning electronics smell is bad. You could disconnect the heating element, tape the fitting so it does not short on something by accident, then use a backflush basket to pressurize the brew system and look for any leaks. A boiler leak would be obvious, you would have staining or a 'crusty buildup' where the water is leaking. On my old Isomac the pressurestat was high in the case, it would be difficult to get water on it other than dripping down from the cup warmer.

If you taker a look at this schematic (millenium, but basically the same as the Tea):
http://users.rcn.com/erics/Illustrations/IS_ELEC3.jpg

It looks like the pressurestat is in the high pressure cutoff (NO) position, which is turning on the green light, but the boiler also has voltage, which is turning on the red light.

Apparently there's a malfunction in the heating circuit - the A2 connection on the SSR can't be getting voltage because the green light is on (check it with a multimeter), but the SSR is engaging. That would lead me to believe that the SSR has gone bad and is keeping the load switch engaged, sending voltage to the heating element, even though there's no voltage going to the control circuit from the pressurestat.

Make sense?

If you're not a customer of Stefano's EspressoCare, you should be. He can help with the troubleshooting, and is happy to do so for his customers. (edit - oops saw you're in Denmark. I'd email him anyway. He frequents these forums and might weigh in)

Thanks for the replies. I have some additional information to add.

So a few hours later I tried turning it on again. This time the green light were 10% lid, however as we got above 1bars pressure it started being fully lid and sometimes blinking. The pressurestat didn't stop the boiler.

If I remove the 'now at 1.2' cable, the green light will show and boiler turned off.
If I remove the no pressure cable, the red light will show and the boiler will continue to run until I turn the machine off.

Or maybe it was the other way around. But it does receive the correct signal. However when the cables are plugged in correctly, it acts like first mentioned.

sebbruhn wrote:If I remove the 'now at 1.2' cable, the green light will show and boiler turned off.
If I remove the no pressure cable, the red light will show and the boiler will continue to run until I turn the machine off.

The designations "now at 1.2" and "no pressure" don't mean anything to me. If you have a CEME pressurestat (it has a yellow top), there are 3 quick connect terminals. One is marked "COM" one "NO" and one "NC". First, what color wires are connected to each one? Second, When you disconnect the one marked "NC" does the heating element stop heating (and the red light go out)? When you disconnect the one marked "NO" does the green light go out?

See the illustrations of the CEME pressurestat and the COM, NO, & NC terminals here:
http://www.chriscoffee.com/kb_results.asp?ID=5

One more thing: Are there 2 blue wires or just 1 connected to the COM terminal? Do the wire connections at the top of the pressurestat look like this:

Sorry for not mentioning, but the replaced pressurestat is a Mater XP110

To sum it up. When turning on the machine, the red led shows displaying that the boiler is on and machine not ready. When the water starts to boil you can hear the 'little thing' closing the tank and it thereby starts building pressure. The green light then immediately shows and the red continue to stay on, making the boiler continue heating. I assume the problem is related to the pressurestat, sending out the wrong message or?

OK. That's fine. I am just trying to determine whether the wires are plugged into the correct terminals, and what happens when you disconnect them. If you look at the photo at the Chris Coffee website, there's annotations of the MA-TER pressurestat that show the equivalent terminals. Is the wire plugged into the top terminal the COM (2 blue wires)? The red should be the middle terminal, and the single blue should be the bottom. What happens when you unplug them as in my previous question?

I'll try and make this easy to read.

• First of all, there is only one cable connected to the com center.

• Second, removing the NO cable result in red light turned on and heating element on. However when archiving boiling temperature and pressure starts to build, the green light will also show. Pressure will continue to rise until turning off the machine.

• Third, removing the NC cable will result in only green light on and heating element off.

• Lastly, removing the COM cable will result in both lights out and also the heating element being off.

Hope this is a better explanation of the situation.

Regards, Seb