BoilerFaultCodes H.....4...... High
Boiler Fault Code H.....4......
Also written as H4 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code H.....4...... appears across 1 boiler brand and 12 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 a safety sensor in the exhaust pipe is reporting an incorrect temperature reading or has developed a fault. (As reported on Ideal Esprit HE)
Pick your boiler brand for the H.....4...... fix
Source
Information for the H.....4...... 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