BoilerFaultCodesGlow-worm F.84 Fault Code
Also written as F84 — same fault.
The Glow-worm F.84 fault code means: your boiler has detected that the sensors measuring the temperature of the water flowing in and out of the system are providing inconsistent or conflicting information, causing it to shut down to prevent damage.. It appears on 17 Glow-worm models in our database.
Technical description: Fault:Flow/returntemperaturesensor
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.84 fault code
Click a model for the full fault code list and model-specific repair notes.
- Betacom4 Repair: £120-£200
- Compact Repair: £150-250
- Easicom3 Combi Repair: £120-220
- Easicom3 System Repair: £120-220
- Energy Repair: £150-250
- Energy Regular Repair: £120-220
- Energy System Repair: £150-250
- Energy7 Combi Repair: £120-220
- Energy7 Regular Repair: £150-250
- Energy7 System Repair: £150-250
- Essential Repair: £150-250
- Flexicom 24c / 28c Repair: £150-250
- MicraCom Repair: £150-250
- Sustain 12s Repair: £120-220
- Ultimate 3 25R Repair: £120-220
- Ultimate3 Combi Repair: £150-250
- Ultimate3 System Repair: £150-250
Source
Glow-worm F.84 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
- Glow-worm Betacom4 manual (PDF)
- Glow-worm Compact manual (PDF)
- Glow-worm Easicom3 Combi manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026