F9 or L9 or F8 or L8 High

Boiler Fault Code F9 or L9 or F8 or L8

Also written as F9ORL9ORF8ORL8 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code F9 or L9 or F8 or L8 appears across 2 boiler brands and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's computer system has lost its settings or is failing to communicate, meaning the boiler cannot safely operate. Because the central control unit is malfunctioning, you will currently have no heating or hot water. (As reported on Ideal Logic Combi ESP1)

Pick your boiler brand for the F9 or L9 or F8 or L8 fix

Ideal F9 or L9 or F8 or L8 3 models Zanussi F9 or L9 or F8 or L8 1 model

Source

Information for the F9 or L9 or F8 or L8 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