BoilerFaultCodesVaillant S.97 Fault Code
Also written as S97 — same fault.
The Vaillant S.97 fault code means: your boiler is performing a routine internal check on its water pressure sensor and should resume normal operation once finished.. It appears on 11 Vaillant models in our database.
Technical description: Water pressure sensor self-test. The self-test for the water pressure sensor is activated.
What causes the Vaillant S.97 fault?
This occurs when the boiler's internal computer performs a safety check to ensure it is receiving an accurate reading from the water pressure sensor. It happens automatically to verify that the system is not running dry, which protects the internal components from overheating. Most often, this is just a momentary pause in operation, but if it persists, it may indicate the sensor is sending inconsistent signals or the wiring has become loose.
DIY fix possible
Wait up to 15 minutes for the automated test to completeCheck if the water pressure is between 1.0 and 2.0 barReset the boiler if the code remains on the screen for a prolonged period
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Vaillant models that show the S.97 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant S.97 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
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Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026