malcolm, I am sure that the diverter valve is faulty,This is the valve that shuts of the heating and diverts the hot water to hot water mod only, but if the diverter valve diaph[rubber disc]
is perished then that is what will not happen, a new kit for this is about £20-00 plus £3-50 for new joint rings, a new complete valve is about £105-00, can be a pig to fit.keep smiling bob roberts ,ps hope this will help you.
bob roberts
January 2006