Medium Warning
7 12 on Ariston Microsystem 15

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.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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 this 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.

Engineer required

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

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Related fault codes

7 11View →7 13View →

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