The S1 Cafe - Helping Your Espresso Dreams Become Reality

Hello all!

I'm aware this post is going to be similar to the one a few down the list. I've read through all of that and have landed here. I really need some solid advice on where to go next.

I have a 3yr old mini 2 which I normally leave on 24/7.

When I travel, I put it in standby and have had no issues at all. However the other day when I returned home from a 3 day trip, I fired up the machine and the steam boiler overheated! The needle wrapped all the way around to the other side of the gauge. I shut it off, but never did get any warnings or release of the OPV. I thought maybe the gauge was faulty at first, but when I opened the steam valve, it came out with more power than I've ever seen on any machine. So I'm guessing it wasn't the gauge. I reset the machine and tried a few more times with the same result.

I called Clive Coffee (where it was purchased) and was instructed to remove the temp probe from the steam boiler and check and clean for scale buildup. However there wasn't any scale, just a little patina. I did clean up the probe and re-install.

I have since reattached everything and fired the machine up to learn something new. Everything heated up just fine. When the steam boiler reached the point that it should shut off, it continued past like before. However this time, after a few seconds I got a blocking alarm and it shut off. This has never happened before. Lights 19-20-21 were lit (Solid). Which I know according to the manual- Steam Boiler Temperature Detection System Failure. This blocking alarm occurs when the temperature probe of the boiler is in short circuit (temperature >145°C) or it is in open circuit (disconnected) condition (temperature <60°C).

I've also tested the temp probe with a multimeter and the resistance was high. Much higher than when I metered the probe on the brew boiler (however I did not remove the brew probe during testing). During testing, I applied heat to the disconnected steam probe (open flame), the resistance fell. Would that mean it's working correctly?

I've also checked the Safety Thermostat, there seems to be continuity through that. Tell me if I'm wrong, but if my understanding is correct, if it were faulty there would be none.

So where would you guys recommend I go from here? Thanks in advance!

I've included a picture of the top of my boiler in case anyone cares to see it. Temp probe is currently removed.

Did you check out the resistance scale in this post? http://s1cafe.com/viewtopic.php?f=57&t=2299#p24390

Your results should be pretty close to what is shown in this table. Plus the sensor is not really intended for use much above normal boiler operating temperatures. If you put fire to it you may have damaged it if it wasn't damaged already.

Farther down in that other thread is my detailed troubleshooting recommendation for steam boiler problems. You should run through that entire process.

Thank you so much for your time Chas! I ran through all of that except metering the heating element with power on. My temp probe metered between 1400-1550 when the chart said it should be 1077. Do you think that would indicate a faulty probe? It measured that before and after I applied heat to it. When I moved the probe close to the flame the resistance fell to about 500.

Based on your measurements the temp sensor is definitely bad.

Chas, new probe has been ordered. I truly appreciate your help. I'll be sure to post results when the replacement arrives.

UPDATE: New temp probe installed. Back to normal! Chas your help is greatly appreciated!

I did notice that a new probe from Chris Coffee does not include the gasket. I called and was told that they are unable find a compatible replacement and they instructed me to make my own from teflon tape, which seems to work fine.

If you're not careful bits of Teflon tape can break off and eventually clog the lines. I usually try tightening nuts without teflon first and only go back and add it if the connection leaks. But if you're careful, no problems.

Glad to hear that you're up and running. Was it the newer short, stubby one or the older type sensor attached to long wires that you have to stick down into a tube? If it is the stubby one, they were having a lot of trouble with failures due to rapid mineral deposits and corrosion. They came up with a new coating that is resistant to that issue and were supposed to have it in stock about now. Hopefully you got one of those.

Good point Chas, The guy at CCS instructed me to not wrap the teflon tape around the threads and instead above the threads so it forms more of a new gasket.

As for the probe itself, it was a newer one, about 1/2" in total length. The original one I pulled out did not have any scale buildup or deposits, but there was a lot of patina. Hopefully this one last a bit longer :) Thanks again for your help!