High
ALL 26 on Sime Murelle HE Regular

Your boiler has detected an issue with one of its internal temperature sensors, which means it has stopped working to prevent potential overheating or inaccurate operation.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

auxiliary sEnsor Error (s3)

From this model's manual
Verified against the Sime Murelle He Regular installation & service manual, page 41.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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