BoilerFaultCodes C(4) High
Boiler Fault Code C(4)
Also written as C4 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code C(4) 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's temperature control dial is no longer reading the heat correctly, causing the system to shut down or behave inconsistently for safety. (As reported on Potterton Flamingo RS40 RS50)
Pick your boiler brand for the C(4) fix
Source
Information for the C(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