Medium Lockout
7 11 on Ariston Challenger 80E

Your boiler is having trouble 'sensing' the temperature of the water returning from your radiators, which prevents it from heating your home 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 1)

What causes this fault?

This fault occurs when the internal computer can no longer read a consistent or accurate signal from the sensor that monitors water returning from your radiators. The most common reason is that the sensor's internal electrical resistance has failed, but it can also be caused by loose or corroded wiring connections inside the boiler.

Engineer required

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

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