If you have a Warmflow boiler then you probably have a Riello RDB or a Riello 40 burner. This fault sounds like a photocell fault.
RDB burner - Take off Red cover and almost in the centre of the burner there is a black wire with plastic ribs on it. Take it out and clean the end of it and repalce.
Riello 40 - Take red box off and your should see the Grey control box. Loosen screw on left side and pull the control box out - it slides out. At the end of the box there is a small white square photocell. Clean and replace.
Restart boiler and that may do the job. Otherwise, replace the photocell and it should work
Thanks
Gordon
www.fixmyoilboiler.com
Belfast
02890 960 630
Gordon at fix my oil boiler. com
October 2009