overheat warning on boiler will not start?

Hello,
I have a alpha combi boiler. Since yesterday, when i try to start the boiler, the flame starts to die down in 5 seconds, there is lot of pattering noise, the flame goes out completely, the pressure moves back and forth for 2 seconds and the overheat thermostat goes red and the boiler goes off. If I press the reset button, the whole above cycle repeats itself. Pls help.

ij
March 2011

either the thermister is faulty (allowing the boiler to overheat) or the overheat stat is faulty, or the pump/fan overrun (cant remember which on this boiler) is not working (again allowing the boiler to overheat)

need more detail as to when the boiler locks out, ie, when running in cycle, or when you shut it off manually, as much detail as you can

T
July 2008