Hi, I have a Potterton Netaheat boiler and although my heating and hot water appear to be working okay, whenever the boiler switches on (for instance if I turn the thermostat up) I've noticed that it comes on for a few seconds and then goes off again. It does this continually. Any ideas

JM, April 2008

Actually what seems to be happening is that the fan on the boiler is coming on and then normally the pilot light would light but this isn't happening then the fan is switching off. A couple of seconds later it tries again and just continues like this. Initially I thought that my radiators weren't affected but they now appear to be cooling down as though the heating were switched off

JM, April 2008