Hello. My Baxi 105e combi will fire up for a few seconds either on hot water or on central heating then it goes out and stops working. Sometimes the flames will dim then go out but it manages to reignite itself for a second or 2 before going out again. It does this 4 or 5 times - with the burners igniting then going out - before stopping all together then the red flame failure light flashes. I have also had the safety thermostat activated light on too. If I leave it for half an hour or so then 'reset' it, I can then repeat this procedure. The boiler is 12 years old. Any ideas what the problem could be? Thank you. Jon