this is a pressure switch fault. If the system pressure in the rads falls by bleeding them or by a leak then top up the pressure via the filling loop(silver flexible pipe normally near boiler) if system is full a quick trick is to turn one of the valves on heating, the bigger 22mm ones to half open, use an allen key its easier. Then retry the boiler by turning it off on mains then back on. The pump should turn and fire up. If it doesnt get a heating engineer not a plumber as they work with boilers more than plumbers
mark mills, January 2010
