Sounds like the hot water thermistor. (located at the rear behind the gas valve. An easy and cheap repair.
Andy the plumber, September 2009
it can be the water pressure too low or the pressure switch inside needs setting corrctly, run the water low and adjust till flame is a nice blue colour
mike, January 2009
probably the air pressure s/w ventury needs cleaning but also possibly a scaled up secondry heat exchanger
john arundel, December 2005
I have this problem too, I was told from a specialist that I need to have shower taps special for combi boiler; the problem is with the taps not the boiler itself. I have not tried this yet.
Nameer, December 2005
Try bleeding your radiators. I had a similar problem and bled the radiators, then realised one was leaking - problem solved.
