What does the Baxi Duo-tec F99 fault code mean?
The F99 fault code on a Baxi Duo-tec boiler indicates an unknown fault related to the domestic hot water (DHW) system. This can result in the boiler being unable to provide hot water, necessitating further investigation to identify the underlying issue.
Common Causes
- Faulty DHW Sensor: A malfunctioning sensor may fail to detect the water temperature accurately, leading to the F99 error.
- Electrical Connection Issues: Loose or damaged wiring connections can disrupt communication between components, causing the boiler to register an unknown fault.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as it may involve complex electrical components and gas safety regulations. Attempting to fix it yourself could pose safety risks.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F99 fault could range from £150 to £300, depending on whether a sensor replacement or wiring repair is needed. This estimate includes parts and labour costs typical for a qualified engineer.