What does the Glow-worm Energy F77 fault code mean?
The F77 fault code on the Glow-worm Energy boiler indicates a problem with the domestic hot water (DHW) diverter valve. This fault typically means that the diverter valve is either stuck or malfunctioning, preventing the proper flow of hot water.
Common Causes
- Stuck Diverter Valve: Debris or mineral buildup can cause the diverter valve to become stuck, leading to a failure in switching between heating and hot water.
- Electrical Fault: A fault in the wiring or the actuator that controls the diverter valve can prevent it from operating correctly.
Can I fix it myself? (DIY)
It is highly recommended to call a Gas Safe Engineer for this issue, as working on gas appliances can be dangerous. Attempting to fix electrical or gas components without proper training can lead to serious safety risks.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for the F77 fault, including parts and labour, is around £150 to £250. This cost reflects the price of a new diverter valve and the expertise required for installation by a qualified engineer.