I have a gas condensing boiler - Potterton F2 50 (10 years old).
The electronic ignition fires a pilot light, the boiler lights, runs for a few minutes then clicks and drops back to pilot light for about 1 min then clicks and restarts. This process will be repeated several times, the boiler may then run normally for a while or switch off. The fault appears to be intermittent and occurs when running either HW or CH or both. PCB was changed about 10 months ago as boiler stopped working altogether. Boiler has been serviced, engineer thinks this may be the gas control valve but does not seem to be confident; he left saying he would source a valve but I have heard nothing more. He also told me that the fan is looking the worse for wear. I am reluctant to chase him up without a better understanding of the possible cause – can anyone advise me over this.