31. High

Saunier Duval 31. Fault Code

Also written as 31 — same fault.

The Saunier Duval 31. fault code means: your boiler has stopped working because a sensor that measures the water temperature has developed an electrical fault and is giving the system a confusing signal.. It appears on 2 Saunier Duval models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: The heating flow thermistor is short circuited.
Typical repair cost £120-200 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Saunier Duval models that show the 31. fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Saunier Duval 31. fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026