BoilerFaultCodesViessmann F.77 Fault Code
Also written as F77 — same fault.
The Viessmann F.77 fault code means: your boiler's internal computer brain is struggling to remember its settings, which means the system cannot start up safely until the memory is checked or restored.. It appears on 4 Viessmann models in our database.
Technical description: Data memory burner control unit
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like F.77: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Viessmann models that show the F.77 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann F.77 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
- Viessmann Vitodens 100-W WB1A manual (PDF)
- Viessmann Vitodens 200-W B2HF System manual (PDF)
- Viessmann Vitodens 200-W B2KF Combi manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026