My Ariston "euro-combi" boiler has an intermittent problem. Sometimes it will take anywhere between two and dozens of attempts to fire up and stay lit. When it does this, the boiler flame lights, but them immediately goes out. It's almost as if the boiler thinks the flame has failed to ignite, when that is clearly not the case. Occasionally the boiler will refuse to fire at all for a period of time.
The symptoms get much worse when the boiler has been recently used - for example one person can have a shower without problems, then five minutes later the next person will find that the boiler will not fire at all. Turning the power to the boiler off and on, or turning the hot tap off and on can encourage it to try to fire again, but frequently it appears that the boiler must cool down before it will fire again and stay lit. The central heating can be affected the same way, but is much less of an issue than the shower going cold half- way through.
I have had this investigated, but without success as the problem is intermittent, and I've so far not been able to reproduce it with a plumber/central heating engineer present. Does anyone have any ideas as to what could be the cause of the problem?
Thanks very much,
Gavin