On Thu, 6 May 2021 18:35:48 +0100, GB
wrote:

Our 23 year old tumble dryer

Well done for keeping it that long. Many would have thrown it away
just because it was 'old'. ;-(

(!) stopped heating the air, although the
rest of it worked.

So, I dismantled it, couldn't find what was wrong, cleaned it, and put
it back together.

It's nice when it's all back and clean isn't it? When I finally
stripped ours just recently I found quite a level of fluff furring on
the insides of some of the ducts that you wouldn't normally be able to
get to *unless* you were really taking it completely to bits (things
that were held on / together / sealed with double sided tape etc).

About 6 hours altogether. It now works perfectly.

Result. ;-)

Please, please reassure me that disconnecting it from the electricity
would not have reset it without all the dismantling?

Erm ... no, *bound* to have been a bad connection on the heater
somewhere. ;-)

I think we have all done that sort of thing and at least yours is
still working. It's worse when you find nothing, break something
*then* find the original cause was something trivial. ;-(

Cheers, T i m