Hi, Had problems with the fan becoming noisy on 7 year old boiler recently, but copper greased it made it much quieter. Now intermittently the boiler won't light. The fan comes on, and spins, the APS click/switches and then I hear/see the clicking of ignition electrode, but no iginition. Then sometimes when I switch the boiler off and back on - everything works normal. Then after 15 mins fails to ignite again. Is it likely to be the related to the fan even though it appears to be working and the APS switches? Or possibly the Gas valve. It is very intermittent. If the fan is on and APS switches is that proof enough that there is enough draw through boiler? This was serviced last month. Appreciate any help.