F.365 Emergency

Viessmann F.365 Fault Code

Also written as F365 — same fault.

The Viessmann F.365 fault code means: your boiler has detected a safety concern where the gas supply system is not switching off correctly, so it has shut down to prevent potential danger.. It appears on 4 Viessmann models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: Burner in a fault state. Gas valve electricity supply does not turn off.
Typical repair cost £200-400 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Viessmann models that show the F.365 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Viessmann F.365 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026