Yesterday, I 'fixed' a storage heater. I didn't post it yesterday, as I wasn't fully sure it would actually work when the Economy 7 turned on, and being a three-element device, it would be a bit iffy to test it via a temporary plug arrangement.
Anyway, it did heat up overnight, so we can rest for a while.
It has two thermal fuses, to protect against overheating, but they are made from materials that aren't really up to it and they have degraded over the years.
The two things at the front here.
This isn't the actual device from yesterday, but it is pretty much what I found. after discovering that the elements all worked and then tracing back the fault to the left-hand 'fuse' at the front.
It's all a little bit Heath Robinson and they will, in fact, no longer sell you the actual replacement parts, but a completely different, and fairly expensive, alternative set-up, though it may be a bit more long-lived. The new arrangement seems to use ceramic* insulators where Bakelite-type stuff has been used here.
Fitting the new arrangement would entail some further dismantling, with its associated risks of creating further damage - so, we'll see what happens first, I think.
I made a few little modifications which seemed to make the cut-out stay closed reliably. The left one was where the real issue was.
Fingers crossed.
Having seen how "ambitious" the general design is, I did make a point of double-checking that the earth connection was fully viable!
* as used on the temperature/output control at the back.