Could you help please, the flame light (green) on my Kingfisher RS50 will not come on as a solid light. It makes a flickering noise and goes on and off constantly. This is on the front panel, next to the lock out button. I cannot see a lit pilot light through the small hole also. When I turn on the water the boiler makes a noise as if it is starting up, but no heat appears. Its the same if I knock on the central heating.