BoilerFaultCodesGlow-worm F.33 Fault Code
Also written as F33 — same fault.
The Glow-worm F.33 fault code means: your boiler has detected an issue with the system that moves air through the unit and is pausing its activity as a safety precaution, meaning you currently have no heating or hot water.. It appears on 11 Glow-worm models in our database.
Technical description: Fanfrostprotectionfunctionactive:Airpressureswitchfault
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.33 fault code
Click a model for the full fault code list and model-specific repair notes.
- Compact Repair: £150-350
- Easicom 2 24c Repair: £150-300
- Energy Repair: £150-300
- Essential Repair: £150-250
- Flexicom 24c / 28c Repair: £150-350
- MicraCom Repair: £150-300
- Sustain 12s Repair: £120-£350
- Sustain 15s Repair: £120-£350
- Sustain 18s Repair: £120-£350
- SUSTAIN 30c Repair: £120-250
- SUSTAIN 35c Repair: £120-250
Source
Glow-worm F.33 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 31 August 2026