Boiler Fault Code 63:1

Also written as 631 — same fault.

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

Fault code 63:1 appears across 1 boiler brand and 5 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is performing a routine automatic safety check and system cleaning once a day to ensure everything is working correctly. (As reported on Viessmann Vitodens 300-W)