What does the Worcester Bosch Greenstar Si F77 fault code mean?
The F77 fault code on the Worcester Bosch Greenstar Si indicates a problem with the system temperature, often related to overheating or a failure in the temperature sensor. This can prevent the boiler from operating efficiently and may require immediate attention to avoid further damage.
Common Causes
- Faulty Temperature Sensor: The temperature sensor may be malfunctioning, providing incorrect readings to the boiler’s control system.
- Blocked Heat Exchanger: A blockage in the heat exchanger can restrict water flow, leading to overheating and triggering the F77 fault code.
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 handling. Attempting to fix it yourself could pose safety risks.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F77 fault could range from £150 to £300, depending on whether the temperature sensor needs replacement or if the heat exchanger requires cleaning or repair.