How much does it cost to fix boiler error code AL21?

Typical repair cost for the boiler AL21 fault is £90-180 including labour.

AL21 High

Boiler Fault Code AL21

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code AL21 appears across 1 boiler brand and 8 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has shut down because a safety device or an external controller has detected an issue and stopped the system from running. (As reported on Vokera Mynute 10E)

Pick your boiler brand for the AL21 fix

Vokera AL21 8 models

Source

Information for the AL21 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 27 April 2026