While you wait for answers, we may have found some information which could help you.
Click here for Saunier Duval Error Code Heating
saunier Duval is over pressurising when the heating is on. ?
Saunier Duval F35E auto-vents down to code 21 in minutes?
I need to find the reset switch ?
'f19' error report - Saunier Duval 'Thermoclassic' boiler?
Saunier Duval Isofast condens F35E....nothing working?
Saunier Duval timeclock not working?