CH/DHW on the blink - turns off after 3 secs

[Tim]

My hot water and central heating Combi will only run for about 3 secs, even after a system reset or power off. When I turn on the tap, the boiler runs, fires up, produces a few seconds of hot water, then turns off. Same with the heating. A reset gets me another few seconds!

Water pressure is OK. The boiler is a Ferroli Domina.

Any idea what the problem is? Can I do anything to work round it in the short term?

Thanks Tim

[NickNoxx]

Sounds like the flame sensor but could be caused by other (more expensive) things too.