I'm new to this forum so please bear with me. I've moved to a new property that has an existing Baxi Combi Instant 105e Boiler. The hot water works fine but when I've tried to fire up the central heating it doesn't work. When I switch on the CH after 10 second the 'hot water tap symbol' flashes green, the ignition flashes yellow then goes solid. After about 12 seconds the 'hot water tap symbol' goes off and then about 30 seconds later the boiler stops. The radiators at no stage heat up. I've looked in the fault finding manual and the according to this the 'radiator symbol' should come on green to begin with instead of the tap symbol. Any suggestions of what the fault might be or anything I can try make it work / diagnose it further?