While you wait for answers, we may have found some information which could help you.
Click here for Heating Boiler Control Circuit Board
saunier Duval is over pressurising when the heating is on. ?
Saunier Duval timeclock not working?
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?
isotwin condens f 35 e service menu codes?