gas hob flame failure sensor problems
 

I've got a Neff gas hob which has a flame failure sensor on each burner.
Just came back from 2 weeks holiday, one of the burners will not stay
lit (was fine before).

Does anyone know how the flame failure devices work so I can try to
diagnose the problem? Do they use electrically operated valves? If I
twang the control knob after it's ignited, sometimes I can get it to
stay lit, so I suspect there is a part of the control valve which should
be opened by the sensor which is sticking. The sensors are small conical
metal things, look like Weller soldering iron tips.
--
Tim Mitchell