What does the Glow-worm Energy F91 fault code mean?
The F91 fault code on the Glow-worm Energy boiler indicates a problem with the domestic hot water (DHW) flame, suggesting that the boiler is unable to establish or maintain a flame for heating water. This can lead to a lack of hot water supply in your home.
Common Causes
- Blocked Flue: A blockage in the flue system can prevent the safe expulsion of combustion gases, causing the boiler to shut down for safety reasons.
- Faulty Flame Sensor: If the flame sensor is malfunctioning or dirty, it may not detect the flame properly, leading to the F91 error code.
Can I fix it myself? (DIY)
It is strongly advised to call a Gas Safe Engineer to diagnose and repair this issue, as it involves gas and electrical components that can be dangerous if handled incorrectly.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F91 fault could be around £150 to £250, primarily depending on whether the flame sensor needs cleaning or replacement, or if there are flue blockages that require professional attention.