How much does it cost to fix boiler error code 123?

Typical repair cost for the boiler 123 fault is £120-200 including labour.

123 Medium

Boiler Fault Code 123

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code 123 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 boiler is confused because it is receiving an incorrect signal from a temperature sensor, which is preventing it from heating your water or home properly. (As reported on Worcester Bosch Greenstar CDi Compact)

Pick your boiler brand for the 123 fix

Worcester Bosch 123 1 model

Source

Information for the 123 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