S 04 Medium

Ariston S 04 Fault Code

Also written as S04 — same fault.

The Ariston S 04 fault code means: your boiler is struggling to detect the temperature of your hot water, which means it cannot provide consistent or safe water for your taps and showers.. It appears on 3 Ariston models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Open circuit on Domestic hot water sensor
Typical repair cost £90-160 (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 04 fault code

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

Source

Ariston S 04 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 31 August 2026