7 12 Medium

Ariston 7 12 Fault Code

Also written as 712 — same fault.

The Ariston 7 12 fault code means: your boiler is having trouble communicating with the temperature sensor for your secondary heating area, which may cause that part of the home to struggle to heat up correctly.. It appears on 6 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: Return sensor defective (zone 2)

What causes the Ariston 7 12 fault?

This fault occurs when the boiler's control board loses communication with the temperature sensor responsible for monitoring water returning from a second heating zone. The most common reason is that the sensor has electronically failed or the electrical wiring connecting it to the main circuit board has become loose or damaged.

This fault is more common in autumn or winter when the heating is first switched on and multi-zone systems are put under constant demand.

Typical repair cost £120-200 (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 7 12 fault code

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

Source

Ariston 7 12 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