How much does it cost to fix boiler error code AL 12?

Typical repair cost for the boiler AL 12 fault is £80-£120 including labour.

AL 12 High

Boiler Fault Code AL 12

Also written as AL12 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code AL 12 appears across 1 boiler brand and 15 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning 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. (As reported on Sime Murelle Pro HE R MkII System)

Pick your boiler brand for the AL 12 fix

Sime AL 12 15 models

Source

Information for the AL 12 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

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