I have recently had a major problem with my Ariston Microgenius 23 Combi boiler (4 yrs old). The landlord turned my water supply off for 2 days while I was away, boiler on timer program. After the water is now back on the boiler has a lot of trouble staying alight. It will turn itself off after 1-30 seconds, sometimes longer. It will then re-light a few more times until either the fume sensor light activates or it will turn itself completely off. After looking at a few forums I think it may be the PCB but can anyone help with any other possiblities and whether I can change the PCB myself (I am an alarm installer for 12 years so knowledge of electronics is good)