ALARM 01 High

Sime ALARM 01 Fault Code

Also written as ALARM01 — same fault.

The Sime ALARM 01 fault code means: your boiler has detected that the exhaust gases are getting too hot, so it has shut down as a safety precaution to prevent damage.. It appears on 1 Sime model in our database.

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.

Technical description: Flue temperature alarm — check flue thermostat link on PCB terminals 54–56
Typical repair cost £120-280 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Sime models that show the ALARM 01 fault code

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

Source

Sime ALARM 01 fault code information on this page is sourced and cross-checked against the official Sime service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026