saborcafe Senior Member Joined: 12 Jun 2011 Posts: 39 Location: MI Expertise: I live coffee
Posted Sun Apr 6, 2014, 10:55am Subject: Charred OverTemp sensor on Nuova Simonelli Mac 2000V?
Hello guys, my machine stopped heating and after further inspection I found the Over temp sensor completely charred. The heating element reads about 8 ohms which is the same reading on my Bezzera machine so that should be good unless it is shorting out at high temperatures. I removed the cover for the P-Stat and the contacts seem a little rough but can be cleaned. None of the other wires seem affected and the circuit board looks nice and clean. No fuses or relays or resistors SEEM bad. I am assuming that the Over temp sensor increases resistance as temperature increases acting as a short when temperatures get too hot but this failure seems to come from over current on the circuit. If the failure was due to Over temp then the ground wire for example would have melted also, right? On the other hand, the other ends of the Over temp wires (heater and P-Stat) are perfectly fine, so the highest resistance was at the Over temp connections?
Can someone help me out in what I should check next and why did this happen? Has anyone ever seen this? Why is it not a fuse or something on the circuit?
skydragondave Senior Member Joined: 18 Feb 2013 Posts: 167 Location: Ontario, Canada Expertise: Professional
Espresso: Commercial Only Grinder: Commercial Only Roaster: Has Garanti HG5
Posted Sun Apr 6, 2014, 12:22pm Subject: Re: Charred OverTemp sensor on Nuova Simonelli Mac 2000V?
The spade terminals on the ends of the wires likely were corroded, creating resistance that overheated them and melted the wires. Replace the hi-limit thermostat, cut the wires back to fresh orange copper, splice in new wires with silicone or hi-heat insulation and high quality spades and retest. If there was a short the wires would have burned up all along their length. Good luck
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