BoilerFaultCodesGlow-worm S.00 Fault Code
Also written as S00 — same fault.
The Glow-worm S.00 fault code means: your boiler is working correctly and is simply resting because your thermostat has reached the desired temperature or the heating is turned off.. It appears on 12 Glow-worm models in our database.
Technical description: no heating required
What causes the Glow-worm S.00 fault?
This status appears when your boiler’s internal computer confirms there is currently no demand for central heating from your room thermostat or programmer. It is the boiler's way of standing by and saving energy because your home has already reached the desired temperature. Once the room temperature drops below your target setting, the boiler will automatically exit this mode and fire up again.
This code is frequently seen during the transition into spring and summer when heating is used less often or turned off entirely.
DIY fix possible
Check that your room thermostat is turned up higher than the current room temperatureEnsure your heating programmer or timer is set to 'On'Check that the thermostatic radiator valves (TRVs) are turned to an open position
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Gas Safe Register →Glow-worm models that show the S.00 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm S.00 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 27 April 2026