On Tue, 21 Jul 2020 16:08:51 +0100, Martin Brown
wrote:

There is a fuseable link inside the little controller which blows if the
thing starts to draw unexpectedly high current or after about 5 years
whichever occurs sooner.

Not a fuseable link - a thermal fuse. Different principle altogether:

https://www.ebay.co.uk/itm/Thermal-T...AOSwAVRde~U F