While you wait for answers, we may have found some information which could help you.
Click here for F4 Combi Boiler
I have a 30cx glowwarm that is showing F4 as fault.I have no hot water?
I have moved into a flat am dissabled carnt get heating on unit flashing F1?
Home heating systems?
BMU error code?
Which way to turn slotted screw to adjust water pressure up on a glow worm ?
Central heating not working?