BoilerFaultCodesViessmann 63:1 Fault Code
Also written as 631 — same fault.
The Viessmann 63:1 fault code means: your boiler is performing a routine automatic safety check and system cleaning once a day to ensure everything is working correctly.. It appears on 5 Viessmann models in our database.
Technical description: Additional function: 1x daily
What causes the Viessmann 63:1 fault?
This code appears when the boiler executes its automated self-maintenance routine designed to protect internal moving parts. It physically cycles the internal pump and valves for a brief moment to prevent them from becoming stuck due to inactivity. This is a normal operational feature and does not indicate that anything has broken or failed.
This is more noticeable during summer months when the heating is rarely used, as the boiler must manually trigger the pump to prevent it from seizing.
DIY fix possible
No action required; this is a normal operating status message rather than a breakdown.Monitor the display to ensure it returns to the standard temperature reading automatically.If the code stays on the screen permanently, try a simple reset.
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Gas Safe Register →Viessmann models that show the 63:1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 63:1 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026