What does the Worcester Bosch Greenstar CDi F91 fault code mean?
The F91 fault code indicates a problem with the feedback system of the boiler, which can affect its ability to operate correctly. This issue may prevent the boiler from firing up or maintaining its operation, leading to heating and hot water supply interruptions.
Common Causes
- Faulty Sensor: A malfunctioning temperature or pressure sensor can disrupt the feedback loop, causing the F91 error.
- Wiring Issues: Damaged or loose wiring connections within the feedback system can lead to incorrect readings and trigger the fault code.
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 pose safety risks.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F91 fault could be around £150 to £250, primarily due to the need for professional diagnostics and potential replacement of sensors or wiring.