8.3 Emergency

Glow-worm 8.3 Fault Code

Also written as 83 — same fault.

The Glow-worm 8.3 fault code means: your boiler is failing to shut down when it reaches the required temperature, which means the water inside may keep heating up unnecessarily.. It appears on 1 Glow-worm model in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: Thermostat Will Not Cut Out
Typical repair cost £150-250 (including labour)

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 8.3 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Glow-worm 8.3 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