What does the Viessmann Vitodens 111-W F79 fault code mean?
The F79 fault code indicates an issue with the modulation of the heating circuit in the Viessmann Vitodens 111-W boiler. This can lead to inefficient heating and may require immediate attention to ensure proper operation.
Common Causes
- Faulty Modulation Valve: The modulation valve may be stuck or malfunctioning, preventing the boiler from adjusting the heating output correctly.
- Sensor Issues: A defective temperature sensor could be providing inaccurate readings, leading to improper modulation of the heating circuit.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as it involves gas and electrical components that require professional expertise. Attempting to fix it yourself could pose safety risks.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F79 fault could range from £150 to £300, depending on whether the modulation valve or sensors need replacement. This estimate includes parts and labour for a qualified engineer.