Hi
This is definately the diverter valve which is at fault, the syncron motor inside has seized and not allowing the valve back into hot water mode, New motor costs £8.50 trade
Hope this helps
Warwick Taylor, March 2008
check. with the heating cold(off for a couple hours til stone cold pipework) run a hot tap and feel the heating pipes under the boiler. if one get hot then divertor valve is allowing heat down the ch instaed of to the dhw exchanger.
please note im guessing its a combi as you never specified boiler/system
iain, March 2008
edit
I can answer this question...
struggling to get hot water,but radiators are hot?