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.
Technical description: Short circuit on heating return sensor
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ariston models that show the E 09 fault code
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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