ravenheat 820/20 combi boiler problem, around 2 months ago my daughter stated that when she turned on her hot water tap, the radiators got warm, diverter valve i suspected, and told her to get someone in and get it sorted, however she did not now everything has packed up, we put the room stat on so it is calling for heat, and the pump runs and the pilot light is alight, but the boiler does not fire up, same with the hot water turn on the tap the boiler does not fire, i stiil believe this damm diverter valve or micro switch has something to do with it, any suggestions would be more than welcome, pump runs, fan runs but boiler does not fire please help