BoilerFaultCodesGlow-worm F.77 Fault Code
Also written as F77 — same fault.
The Glow-worm F.77 fault code means: your boiler has detected an issue with the system that removes waste gases, meaning it cannot operate safely and has shut itself down to prevent a fire or carbon monoxide hazard.. It appears on 19 Glow-worm models in our database.
Technical description: Fault: Condensate or smoke. No response, flue non-return flap defective
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Glow-worm models that show the F.77 fault code
Click a model for the full fault code list and model-specific repair notes.
- 30cxi Repair: £90-250
- 38cxi Repair: £90-180
- Betacom4 Repair: £120-250
- Compact Repair: £150-350
- Easicom3 Combi Repair: £120-250
- Easicom3 System Repair: £180-350
- Energy Repair: £120-250
- Energy Regular Repair: £150-350
- Energy System Repair: £120-250
- Energy7 Combi Repair: £150-350
- Energy7 Regular Repair: £150-350
- Energy7 System Repair: £120-250
- Essential Repair: £120-250
- Flexicom 24c / 28c Repair: £150-300
- MicraCom Repair: £150-300
- Sustain 12s Repair: £140-£320
- Ultimate 3 25R Repair: £150-300
- Ultimate3 Combi Repair: £120-250
- Ultimate3 System Repair: £120-250
Source
Glow-worm F.77 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026