BoilerFaultCodesViessmann 1F Fault Code
The Viessmann 1F fault code means: your boiler has stopped working because the burner isn't lighting correctly, likely due to a problem with the internal airflow or the ignition system.. It appears on 1 Viessmann model in our database.
Technical description: Burner blocked
What causes the Viessmann 1F fault?
This fault occurs when the boiler's control system detects that the burner cannot sustain a stable flame after several attempts. It is usually caused by a lack of proper airflow or an issue with the sensors that verify the flame is safe to stay on. The most common reasons are worn-out ignition components or a build-up of debris within the burner chamber that prevents a clean light-up.
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 1F fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 1F 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