BoilerFaultCodes F4 Or L4 High
Boiler Fault Code F4 Or L4
Also written as F4ORL4 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F4 Or L4 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 stopped working because it is having trouble reading the temperature of the water flowing through it, so it has safely shut down to prevent overheating. (As reported on Ideal Logic Combi C24 C30 C35)
Pick your boiler brand for the F4 Or L4 fix
Source
Information for the F4 Or L4 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