"N_Cook" wrote in message
...
On 14/03/2016 16:56, Jeff Wisnia wrote:
Over the years I've had to replace maybe a half dozen thermal fuses
which appear to have failed without ever being heated beyond their rated
temperatures.

Most recently a small electric space heater used in our office under my
desk stopped working because its thermal fuse had opened. The fuse was a
MICROTEMP G4A0 121 degree C unit, and I'm pretty sure that nothing had
blocked air passage through the heater and caused its internal
temperature to rise enough to open the thermal fuss.

Jeff



They also have a current limit , but I do believe than can fail by
deterioration or something

All fuses die eventually, but in most cases they outlive the equipment.

Once or twice I've even seen corrosion kill a fuse, but most thermal types
are in sealed encapsulation. That would be an unlikely failure mode.