Boiler Fault Code 9.iii

Also written as 9III — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code 9.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 overheating because it is burning more gas than it can safely process, causing the internal system to shut down to prevent damage. (As reported on Chaffoteaux Sterling FF)