terrycuttlefish

I have come across a worcester 24i boiler,the problem is the time clock does not keep the time,it does not move.When you have the clock set to manual or auto nothing happens on the central heating.When you turn hot water on the boiler kicks in,gives you hot water and if the central heating is set to manual once the hot water is turned off the boiler keeps on and runs the central heating but once you turn central heating off it does not kick in unless the hot water is run.any help would be great.