Please can anyone help? My boiler central heating wall switch was worn out and wouldn't fire up the boiler. I resorted to putting on both the central heating and hot water switches on at the same time so that the boiler fired up. Shortly after, the hot water when hot will shut the system down and the radiators will cool after a brief period. Now when I switch on the boiler instead of firing up it starts making very violent rattling noises and I immediately switch it off! Do you have a clue what the problem might be.