High
AL 12 on Sime Murelle Pro HE R MkII System

Your boiler's computer has been set to the wrong ventilation mode, causing it to shut down for safety because it thinks it is installed in a different type of building setup.

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

Incorrect configuration of the open/sealed chamber — set parameter PAR 04 (Combustion configuration) to 0 for sealed chamber

From this model's manual
Verified against the Sime Murelle Pro He R Mkii System installation & service manual, page 40.
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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Related fault codes

AL 01View →AL 02View →AL 11View →

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