How much does it cost to fix boiler error code F77?

Typical repair cost for the boiler F77 fault is £120-250 including labour.

F77 High

Boiler Fault Code F77

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code F77 appears across 2 boiler brands and 17 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected an issue with the system that removes waste water or measured a temperature imbalance, causing it to shut down as a safety precaution. (As reported on Glow-worm Ultracom 24cx 30cx)

Pick your boiler brand for the F77 fix

Glow-worm F77 9 models Heatline F77 8 models

Source

Information for the F77 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026