In article ,
David wrote:
On Monday, 10 May 2021 at 15:20:58 UTC+1, Dave Plowman (News) wrote:

Not quite sure how they work? It appears to be just a metal (of some
sort) rod set in a porcelain insulator, and no ground connection.

As I understand it, the flame is full of ions. A small amount of
current can flow from the rod to ground through the flame (if it's
there).

That would explain the problem with it being dirty. But not why they
changed the design slightly. The original started giving problems when the
boiler was near new. The replacement has done 10 years plus without being
touched.

Having cleaned the old one with wire wool, it's now working normally
again. The new sensor arrived yesterday, so I'll keep it as a spare.

--
*I got a job at a bakery because I kneaded dough.*

Dave Plowman London SW
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