worcester 28i junior no hot water?

can anybody help please, ive just fitted a 28i junior,i bought this boiler 3 years ago but only just fitted it due to having an extension.
the central heating works fine but have no dhw,the fan starts when hot water tap is switched on but fan slows and stops and i dont get any hot water atall

any sugestions will be appreciated {will get the wife of my back}