Got summoned by SWMBO to investigate the case of the gas oven not
fulfilling its number one purpose for being...

Symptoms seem to be:

It had preheated and was running ok. Set to gas mark 8 it had been on
for 20 - 30 mins when the igniter started sparking intermittently. The
rate of ignition attempts increased until almost constant. At this point
she turned it off and called me. I relit it, and it went into pre-heat
ok, and appeared to be working normally again[1]. However, shortly after
it resumed the previous behaviour. SWMBO also reported a smell of
unburnt gas which would suggest a genuine flame failure. She found that
if it was turned down to gas mark 6, then it stopped attempting to
ignite, but going back to mark 8 caused a resumption of the problem.

So, likely causes? What to investigate next?

Oven is in a Parkinson Cowan "slot in" cooker. Approx 14 years old.

[1] Although I did not actually test the gas pressure at the time, I did
verify that there was no apparent drop in flame height when the boiler
kicked in for HW production (35kW).


--
Cheers,

John.

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