How much does it cost to fix boiler error code 40 Flashing?

Typical repair cost for the boiler 40 Flashing fault is £120-200 including labour.

40 Flashing Low

Boiler Fault Code 40 Flashing

Also written as 40FLASHING — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 40 Flashing appears across 1 boiler brand and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is struggling to read the outdoor temperature, which means it cannot automatically adjust your heating to match the weather conditions. (As reported on Heatline Capriz 25 System)

Pick your boiler brand for the 40 Flashing fix

Heatline 40 Flashing 2 models

Source

Information for the 40 Flashing 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