I have identical gas boilers working together for the central heating and hot water, and one has stopped working. The fan goes on, pilot starts to spark after 10 seconds or so after the boiler is turned on, but there is no pilot light and the boiler does not go on. As far as I can tell, the gas control valve (pilot and main gas) is getting power from the electronic control box, and I assume the boiler is getting water and gas as it is right next to the working boiler and there is no valve in between the two. Is it likely to be that the pilot control valve is faulty? Is the control valve the same as the pilot solenoid? If so, is changing the gas control valve something which can be done by an amateur?