While you wait for answers, we may have found some information which could help you.
Click here for Error Fault BoilerHow to repair F4 code?
'f19' error report - Saunier Duval 'Thermoclassic' boiler?
saunier duval boiler problem?
Saunier Duval timeclock not working?
Saunier Duval F35E auto-vents down to code 21 in minutes?
isotwin condens f 35 e service menu codes?