Boiler Fault Code Frequent sooting (3)

Also written as FREQUENTSOOTING3 — same fault.

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

Fault code Frequent sooting (3) appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is not burning fuel efficiently, leading to a dangerous build-up of debris inside that prevents it from heating your home properly. (As reported on Chaffoteaux Flexiflame 140)