BoilerFaultCodes 5.iii Medium
Boiler Fault Code 5.iii
Also written as 5III — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 5.iii 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 provide hot water because the debris filter that cleans the water entering the system has become clogged, restricting the flow. (As reported on Chaffoteaux Sterling FF)
Pick your boiler brand for the 5.iii fix
Source
Information for the 5.iii 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