What does the Viessmann Vitodens 100-W F64 fault code mean?
The F64 fault code on the Viessmann Vitodens 100-W indicates a problem with the domestic hot water (DHW) demand. This typically means that the boiler is not receiving a signal to heat water, which can affect hot water availability.
Common Causes
- Faulty DHW Sensor: A malfunctioning sensor may fail to detect the demand for hot water, leading to the F64 error.
- Wiring Issues: Damaged or loose wiring connections between the boiler and the DHW system can interrupt communication, causing the fault code to appear.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as it may involve electrical components and gas safety regulations. Attempting to fix it without proper training can be dangerous.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F64 fault could range from £150 to £300, depending on whether a sensor replacement or wiring repair is needed. This estimate includes parts and labour for a qualified engineer.