While you wait for answers, we may have found some information which could help you.
Click here for Help Leaks ShowersSaunier Duval timeclock not working?
Saunier Duval Isofast condens F35E....nothing working?
isotwin condens f 35 e service menu codes?
I have a Saunier Duval Isotwin condens F 35 E with hot water No heating?
Saunier Duval F35E auto-vents down to code 21 in minutes?
saunier Duval is over pressurising when the heating is on. ?