While you wait for answers, we may have found some information which could help you.
Click here for Central Heating Hot Water Working FineI have a Saunier Duval Isotwin condens F 35 E with hot water No heating?
saunier Duval is over pressurising when the heating is on. ?
saunier duval boiler problem?
Saunier Duval F35E auto-vents down to code 21 in minutes?
Saunier Duval timeclock not working?
isotwin condens f 35 e service menu codes?