Since turning timer off but leaving boiler on winter setting I now find that boiler only fires up 1 in 2 times when I turn on hot water. Stangely , it may work straight away at 6.00 am but not at 9.00am and vice versa. Driving me mad. Discovered that if I put heating on, run tap slowly water is hottish. I am afraid if I book an apointment for engineer to call, symptons may not be there and I am still lumbered with a call out fee. Any ideas please?

Simon n., May 2008

Sounds like the dhw flow switch / turbine is not operating correctly (ie detecting the flow when you turn the tap on)

Other than that, it can sometimes be the inline mains water filter feed to the boiler is partially blocked, reducing flow in turn affecting the dhw flow switch...

T, May 2008