While you wait for answers, we may have found some information which could help you.
Click here for Saunier Duval BoilerSaunier Duval timeclock not working?
Saunier Duval Isofast condens F35E....nothing working?
How can I fix my Saunier Duval Semia Condens boiler?
Saunier Duval Thema F23 anyone have a link for manual?
How to repair F4 code?
'f19' error report - Saunier Duval 'Thermoclassic' boiler?