I wanted to see how these thermal fuses worked inside.
It appears to be two wires held in place with a high temperature resin base, and bridged with a low melting temperature solder surrounded by flux.
When the rated temperature is exceeded the solder bridge melts and the flux causes it to retract into a ball at each side, breaking the circuit.
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https://www.youtube.com/watch?v=S_4xjFRW__U