The New Hotness

A bit less than a year after replacing all the thermal switches / cutoffs / thermostats in the Whirlpool clothes dryer, the Thermal Cutoff went open-circuit. It’s located at the top of the heater duct:

The wiring diagram lists it as tripping at 350 °F and “NOT RESETTABLE”:

Curiously, the replacement switch had only one mark:

I find it difficult to believe anybody would build a thermal cutout at 309°F = 154 °C.

Crushing it with a Vise-Grip reveals the interior:

I don’t know what permanently opens the circuit in there, but it definitely happened. The contacts remain unblemished, so they were pressed firmly together until the end.

With nothing to lose, I reinstalled the Thermal Cutoff I removed last year (*) and the dryer works fine again.

It is possible lint accumulating in the filter bag I added to the exhaust vent restricted the airflow enough to overheat the cutoff, but the Operating Thermostat should keep the air around 155 °F and the Hi Limit thermostat should have tripped at 250 °F, long before the temperature reached 350°F.

Another cutoff will arrive shortly and will remain in the Box o’ Dryer Parts against future need.

(*) Which is why I keep the old parts around, because a dubious part on hand is much better than the new part I might not be able to get due to, oh, “supply chain issues”.