BoilerFaultCodes 86 H.....3..... Medium
Boiler Fault Code 86 H.....3.....
Also written as 86H3 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 86 H.....3..... appears across 1 boiler brand and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is struggling to accurately measure the temperature of your hot water, which may cause your taps to run cold or the water temperature to fluctuate. (As reported on Ideal Isar HE)
Pick your boiler brand for the 86 H.....3..... fix
Source
Information for the 86 H.....3..... 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