BoilerFaultCodes 10.ii High
Boiler Fault Code 10.ii
Also written as 10II — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 10.ii appears across 1 boiler brand and 3 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 maintain a steady temperature and is rapidly turning itself on and off because a internal safety sensor is incorrectly reporting that the system is overheating. (As reported on Chaffoteaux Celtic 2 24 Rsc)
Pick your boiler brand for the 10.ii fix
Source
Information for the 10.ii 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