How much does it cost to fix boiler error code 109?

Typical repair cost for the boiler 109 fault is £150-300 including labour.

109 High

Boiler Fault Code 109

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 109 appears across 4 boiler brands and 10 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected an internal system error that is preventing it from operating safely, causing it to shut down to protect itself. (As reported on Main Insul 7)

Pick your boiler brand for the 109 fix

Ariston 109 1 model Main 109 1 model Navien 109 7 models Worcester Bosch 109 1 model

Source

Information for the 109 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