- I accidently asked this question as an answer. Here it is again.

-My central heating is working OK.
-If I just require Hot water, The boiler lights-up and the upper red neon indicate temp is building, then they all suddenly start flashing insanely (all red neons), then go off - no hot water.
- This happens with increasing frequency (i.e. not all of the time)

what is wrong, the boiler is 4 years old and just out of guarantee! Has the obsolesce chip just kicked in?

Robin Brown, April 2010

Sound like the PCB controller

Recently replaced mine for the same problem

Frank Bird, June 2010

it sounds like ur boiler is full of scale and rust, u possibly require a poweerflush, call if u need assistance on 07716249796 ta

Ammo, April 2010