sounds like you have a problem with the diverter valve,if the mains pressure is ok, always check that all other taps are off and not dripping(in this weather check any outside taps haven't frozen and cracked)if you look under the boiler you can see the brass diverter with a switch on the right hand side,there is a rod with a black cap on which should move in and out when the hot tap is switched on and off to make a micro switch which then starts the boiler fan ect check this first,if the switch is not being made replace the div valve, hope this helps
jim, February 2009
