E66 High

Ariston E66 Fault Code

The Ariston E66 fault code means: your boiler has stopped working because it is unable to accurately measure the temperature of the water being sent to your radiators, causing it to shut down for safety.. It appears on 3 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: Heating flow temperature probe
Typical repair cost £120-200 (including labour)

Engineer required

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

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Ariston models that show the E66 fault code

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

Source

Ariston E66 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