BoilerFaultCodesViessmann 59 Fault Code
The Viessmann 59 fault code means: your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit, usually due to a fault in a sensor or its wiring.. It appears on 8 Viessmann models in our database.
Technical description: No DHW heating: Cylinder temperature sensor 2 lead break
What causes the Viessmann 59 fault?
This fault occurs when the boiler's control board loses communication with the sensor that monitors the heat of the water leaving the unit. It is usually caused by a physical break in the internal wiring or the sensor itself failing due to wear and tear. Because the boiler cannot safely confirm the water temperature, it shuts down to prevent the system from overheating.
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 59 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 59 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