S.36 Low

Glow-worm S.36 Fault Code

Also written as S36 — same fault.

The Glow-worm S.36 fault code means: your boiler is working correctly, but it is currently sitting in standby because your thermostat or external timer is not telling it to turn on.. It appears on 12 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: No Heating demand from external controls 24V

What causes the Glow-worm S.36 fault?

This status occurs because the boiler is waiting for a signal from your external controls to start heating. It usually means your room thermostat is set too low, the programmer is in an 'off' period, or the batteries in your wireless controller have run out. While the boiler is powered and ready to go, the connection from your wall thermostat is currently telling it to stay in standby mode.

This is frequently seen during the transition into autumn when homeowners forget to replace thermostat batteries or update their timer schedules for the colder weather.

Typical repair cost £0-120 (including labour)

DIY fix possible

Check that your room thermostat is turned up higher than the current room temperature.Ensure your heating programmer or timer is set to 'On' or 'Auto'.Replace the batteries in your wireless thermostat if the screen is blank or showing a low battery symbol.

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Glow-worm models that show the S.36 fault code

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

Source

Glow-worm S.36 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