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

Typical repair cost for the boiler Fault 12 fault is £120-£280 including labour.

Fault 12 High

Boiler Fault Code Fault 12

Also written as FAULT12 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

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

Most common meaning Your hot water tank has overheated and a safety switch has shut the system down to prevent damage. (As reported on Worcester Bosch Greenstar CDi Compact)

Pick your boiler brand for the Fault 12 fix

Worcester Bosch Fault 12 1 model

Source

Information for the Fault 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 27 April 2026