BoilerFaultCodesViessmann F.73 Fault Code
Also written as F73 — same fault.
The Viessmann F.73 fault code means: your boiler's internal computer parts are struggling to talk to each other, which means the system has shut down as a safety precaution.. It appears on 3 Viessmann models in our database.
Technical description: Internal communication error
DIY fix possible
Locate the power switch for the boiler and turn it off for 30 secondsTurn the power back on and wait for the system to rebootIf the code persists, press the Reset button on the control panel once
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Viessmann models that show the F.73 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann F.73 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 31 August 2026