BoilerFaultCodesViessmann F.74 Fault Code
Also written as F74 — same fault.
The Viessmann F.74 fault code means: your boiler has detected that the water pressure in the system is too low to operate safely, causing it to shut down to prevent damage.. It appears on 4 Viessmann models in our database.
Technical description: System pressure too low; burner blocked, pump off
DIY fix possible
Locate the external filling loop (usually a silver flexible hose under or near the boiler).Open the one or two taps on the filling loop slowly until you see the pressure gauge rise.Close the taps tight once the pressure reaches 1.5 bar, then reset the boiler.
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Viessmann models that show the F.74 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann F.74 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