I have a systen boiler Ideal minimiser SE. I can only get hot water when the Heating is on! (it didnt used to be the case) If i put the hot water on alone, it doesnt fire up the boiler. If the C/H is on then i get hot water when i turn the water on. I tried changing the programmer but that had no effect. I can hear the diverter valve moving when i turn thr water on and off . Any ideas anybody????