Hi My Dad has a Ferroli optimax 25 c combi boiler which he's had for about 4 years and its just packed up.. When you switch it on by the mains switch it starts to boot up but then just stops and fault code f33 flashes. We have checked the manual and searched the net but can't find an f33 fault code listed anywhere. Can anyone point us in the right direction or better still know what the code means. Thanks.