Hi All,
I know this is a very old thread, but I found it useful, and I believe I have a solution to the problem of this "non-resettable" fuse...and so I post anyway.
I was just checking the parts in my microwave as long as I had it open (the magnetron was clearly burnt).
I checked one temperature switch by placing it on a hotplate burner while contacting the spade connectors with my multimeter set to beep for continuity. Since it was an NO (normally open) switch, the meter was silent until I heard a loud click in the switch followed immediately by the beep of the meter. I had to wait a surprisingly long time for the switch to cool down and reopen, but it did.
The next temperature switch (the exact one mentioned in this thread) I checked the same way, but this one was NC (normally closed). So when I followed the same method, the meter kept beeping until the switch got hot, the loud click sounded, and the meter went silent. However, the switch would not reclose even after cooling to room temperature.
That's what prompted me to go searching online for a new switch and found this thread. To my chagrin, I discovered that this is a one-time, non-resettable switch. Then I looked closer at the stamped numbers on the face of the sensor, which read "N120" then "0" on the next line. I thought, "Why specify the trigger temperature (120°C) and also another temperature (0°C)? Maybe that's the reset temperature!"
Sure enough. I put the switch in my freezer for a while. When I took it out, the switch had closed! So these aren't non-resettable throw-aways after all. I'm glad I didn't order an expensive replacement, because the old one works fine, after all.
Hope this helps--maybe not the OP nor the timely responders, but others who may be coming later looking for a solution as I was.