BoilerFaultCodesGlow-worm 15 Fault Code
The Glow-worm 15 fault code means: your boiler is unable to correctly control the supply of gas it needs to create a flame, causing the system to shut down for safety.. It appears on 12 Glow-worm models in our database.
Technical description: Gas mechanism fault
What causes the Glow-worm 15 fault?
This fault occurs when the boiler's control board fails to communicate effectively with the gas valve, meaning the system cannot safely regulate the fuel flow. The most common reason is an internal electrical failure within the gas valve itself or a fault on the main circuit board that prevents it from sending the correct signals. In some cases, damaged or loose wiring between these two major components is responsible for the breakdown.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A cover plan would handle faults like 15: no call-out fees, no surprise bills.
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Glow-worm models that show the 15 fault code
Click a model for the full fault code list and model-specific repair notes.
- 18si Repair: £180-280
- 23c Repair: £180-300
- 30ci Plus Repair: £180-320
- Ci Plus Repair: £180-320
- Ci Range Repair: £180-280
- Compact (2006-2011) Repair: £150-250
- CXi / CSi Repair: £150-250
- EnergySaver Combi Repair: £250-£450
- Xtrafast 120 Repair: £180-350
- Xtrafast 96 Repair: £180-350
- Xtrafast 96 120 Repair: £180-350
- Xtramax HE Repair: £140-£260
Source
Glow-worm 15 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