E 09 High

Ariston E 09 Fault Code

Also written as E09 — same fault.

The Ariston E 09 fault code means: your boiler has stopped working because one of its internal temperature sensors has developed an electrical fault and can no longer monitor the water coming back from your radiators.. It appears on 7 Ariston 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: Short circuit on heating return 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 E 09 fault code

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

Source

Ariston E 09 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