How much does it cost to fix Ariston error code S 31?

Typical repair cost for the Ariston S 31 fault is £100-180 including labour.

S 31 Low

Ariston S 31 Fault Code

Q: What does the Ariston S 31 fault code mean?

Your boiler is struggling to read the temperature from an outdoor sensor due to a loose wire or faulty connection, so it has reverted to a default setting.

Also written as S31 — same fault.

The Ariston S 31 fault code means: your boiler is struggling to read the temperature from an outdoor sensor due to a loose wire or faulty connection, so it has reverted to a default setting.. It appears on 5 Ariston models in our database.

Technical description: External sensor short circuit

Typical repair cost £100-180 (including labour)

Engineer required

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

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Ariston models that show the S 31 fault code

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

Source

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

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026