I've got a twelve or thirteen year old Prima F which has run reliably until the last year or so. I fixed the usual cycling problem using new high temp capacitors about two months ago. Now the boiler ingnites correctly, but the main burner goes off after a few seconds. The boiler then re-ignites the main burner and again it switches itself off. Sometimes the main burner will remain lit and the boiler provides hot water and or heating according to stats and settings. When the main burner is igniting and then turning off after a few seconds, the boiler pilot light remains lit. Any ideas?
I'd just like to know what might be the problem so I don't look like a complete muppet when I get a corgi in to fix it.
Thanks

jnib, January 2009

between the pressure switch, in the air pipe is a joint made off brass with a small hole in it it could be blocked or have condensate in it

jm law, January 2010

why do you think you would look a muppet to a corgi engineer who you are paying to sort it out ? anyway in answer to your question it sounds like a rectification problem so you might try replacing the ionisation probe/pilot assy...just a few quid

mark the gay boiler man, January 2009

See
http://www.howtomendit.com/answers.php?id=26383
or need to check 240 volts at gas valve if so check resistance of coil on gas valve

a, January 2009