we're having a trouble keeping the boiler lit; it relights happily,
stays a light for usually a minute or so though sometimes quite a lot
longer, then goes out, with the shutoff clunk following just afer the
burner goes out. there's a tinge of yellow on one or two flames from
time to time. the fact that it stays alight and shuts off promptly
makes me think it's not the thermocouple. it's not a very cold night.
Does it sound like a gas valve problem or something worse?

And this might sound mad, but could the electromagnet in the gas valve
be affected by magnets on the boiler case? we moved them all there from
the fridge ;-)

thanks!
Mary