Brian Gaff pretended :
These things are designed to not get hot, if they do then they will be
faulty. All a dropper will do is make a lot of heat wherever you site it,
what is the point of that. I don't know how these devices work but it might
well be that the actual mechanism has become stiff and hence caused the
failure.

Quite the contrary, they are designed to get hot. The heat melts a high
expansion wax, which pushes out a plunger. The work in a similar way to
the wax thermostat used in car engine cooling systems - heat in the
coolant, opens the valve. In this case a tiny heating element heat the
wax, causing a plunger to extend, this then opens the fan cowl up.

It is designed to work with 120/240v and has heat destroyed it, my idea
is to fit a replacement but halve the 240v here, to average 120v, using
a 1N4007 diode. It will no doubt open up little slower, but no problem.