S.05 Low

Glow-worm S.05 Fault Code

Also written as S05 — same fault.

The Glow-worm S.05 fault code means: your boiler is simply cooling itself down after finishing a heating or hot water cycle and will restart normally once it has finished.. It appears on 30 Glow-worm models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: pump / fan overrun

What causes the Glow-worm S.05 fault?

This occurs when the boiler has reached its required temperature and needs to shift excess heat away from the internal heat exchanger. The pump and fan continue to run for a short period to prevent the unit from overheating and to protect the internal components. It is a natural part of the boiler's operating cycle and indicates the system is managing its temperature correctly.

DIY fix possible

Wait for the boiler to complete its cooling cycle, which usually takes several minutes.Ensure your internal radiator valves (TRVs) are open to allow water to circulate.Check that the system pressure is between 1.0 and 1.5 bar on the display.

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Glow-worm models that show the S.05 fault code

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

Source

Glow-worm S.05 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