What does the Glow-worm Ultimate F77 fault code mean?
The F77 fault code on the Glow-worm Ultimate indicates a problem with the domestic hot water (DHW) sensor. This issue typically affects the boiler’s ability to accurately measure water temperature, leading to potential heating inefficiencies.
Common Causes
- DHW Sensor Failure: The sensor may be faulty or damaged, preventing it from providing accurate temperature readings.
- Wiring Issues: Damaged or loose wiring connections to the DHW sensor can disrupt the signal, causing the fault code to appear.
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 may pose safety risks.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for the F77 fault code is around £150 to £250, primarily due to the cost of replacing the DHW sensor and any necessary labour charges.