How can I fix the timer on a Vaillant 282E turbo max?

The timer on my Vaillant 282E Turbo max, no longer fires the boiler, although the boiler itself does work and can be switched on and off manually. Can anyone suggest a likely cause and/or solution.
With thanks
Mr G P Gawin, December 2005


done
Change the time clock

Lee, January 2006
link Click here to see other fixes for Vaillant.