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 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's main internal computer is failing to communicate correctly with its internal control systems, preventing it from safely starting up. (As reported on Ideal Logic Combi C24 C30 C35)

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

Ideal 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 27 April 2026