How can I fix my vokera Linea 24 boiler?

When I switch on the taps the boiler kicks in. When I recently turned the switch over to include the water & heating and then tested the heating, the boiler does not fire up. Works fine for water but no reaction for heating!!!
What is the problem please as I had my Vokera serviced 6 mths ago and dont want to pay out AGAIN.
Dom, August 2009


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