S.00 Low

Heatline S.00 Fault Code

Also written as S00 — same fault.

The Heatline S.00 fault code means: your boiler is currently in standby mode because it has not received a signal from your thermostat or timer to turn on the heating.. It appears on 7 Heatline 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: No request for heating

DIY fix possible

Check your room thermostat is set to a higher temperature than the current room temperatureEnsure your external programmer or timer is set to an 'on' periodCheck that your boiler's internal heating dial is turned up

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Heatline models that show the S.00 fault code

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

Source

Heatline S.00 fault code information on this page is sourced and cross-checked against the official Heatline service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026