Boiler Fault Code F.399

Also written as F399 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code F.399 appears across 1 boiler brand and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected an internal error preventing the burner from lighting, which means your heating and hot water will not work until the fault is cleared. (As reported on Viessmann Vitodens 200-W B2HF System)