How much does it cost to fix boiler error code L (Flashing)?

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

L (Flashing) High

Boiler Fault Code L (Flashing)

Also written as LFLASHING — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code L (Flashing) 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 has detected that the electrical supply is incorrectly connected and is refusing to start as a safety precaution. (As reported on Potterton Envoy 30)

Pick your boiler brand for the L (Flashing) fix

Potterton L (Flashing) 1 model

Source

Information for the L (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