What does the Worcester Bosch Greenstar CDi F77 fault code mean?
The F77 fault code indicates that the boiler has detected faulty environmental conditions, which may include issues with the flue system or inadequate ventilation. This fault prevents the boiler from operating safely and efficiently.
Common Causes
- Blocked Flue: A blockage in the flue can prevent proper ventilation, leading to unsafe operating conditions.
- Inadequate Air Supply: Insufficient air supply to the boiler can trigger the F77 fault, as the system requires proper airflow for combustion.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer to address this issue, as it involves safety-critical components. Attempting to fix flue or ventilation issues without proper training can be dangerous.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F77 fault could range from £150 to £300, depending on whether a flue blockage needs clearing or if additional ventilation is required. This cost reflects the complexity of diagnosing and rectifying environmental issues safely.