BoilerFaultCodes F5 or L5 High
Boiler Fault Code F5 or L5
Also written as F5ORL5 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F5 or L5 appears across 2 boiler brands and 5 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 a sensor that measures the temperature of the water returning to the system is providing an incorrect reading or no signal at all. (As reported on Ideal GB24 / GB30)
Pick your boiler brand for the F5 or L5 fix
Source
Information for the F5 or L5 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