How can I get hot water? ?

I cannot get any hot water and whatever setting I put the Tempus 3 programmer on it does not fire up the boiler - Potterton Prima. I have checked and the electricity supply to the programmer is good so I am wondering if the programmer has packed up.

My question is, is it likely that its the programmer at fault and not the boiler and by simply replacing the Tempus 3, will solve the problem ?

Thanks