What does the Baxi Duo-tec F77 fault code mean?
The F77 fault code on a Baxi Duo-tec boiler indicates a fault with the domestic hot water (DHW) timer. This typically means that the boiler is unable to properly control the timing for heating water, which can affect hot water availability.
Common Causes
- Faulty DHW Timer: The timer may be malfunctioning or damaged, preventing it from accurately controlling the hot water heating schedule.
- Wiring Issues: Damaged or loose wiring connections related to the DHW timer can disrupt its functionality, leading to the fault code being displayed.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as it involves electrical components and gas safety regulations. Attempting to fix it yourself could be dangerous.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F77 fault could be around £150 to £250, depending on whether the DHW timer needs to be replaced or if wiring repairs are required. This cost reflects the price of parts and labour for a qualified engineer.