BoilerFaultCodesViessmann 50 Fault Code
The Viessmann 50 fault code means: your boiler has stopped providing hot water because the internal sensor that measures water temperature has detected a technical fault or a short circuit.. It appears on 9 Viessmann models in our database.
Technical description: Burner blocked. Short circuit - DHW temperature sensor (combi boiler).
What causes the Viessmann 50 fault?
This fault occur when the boiler's control board receives an impossible electrical signal from the Domestic Hot Water sensor, suggesting the component has failed internally. It is usually caused by a 'short circuit' where the sensor's internal wiring has degraded or succumbed to moisture, preventing the boiler from safely monitoring how hot your water is. In some cases, the issue may also lie with a loose or damaged cable harness connecting the sensor to the main computer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Viessmann models that show the 50 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 50 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