Medium Warning
12 on Alpha E-Tec Regular

Your boiler has lost connection with the sensor that monitors the temperature of your hot water cylinder, meaning it may not know when to heat your water.

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

Cylinder sensor fault (FlowSmart only)

What causes this fault?

This fault occurs when the main control board can no longer detect an electrical signal from the temperature probe attached to your hot water tank. It is usually caused by the sensor internal components failing over time or a loose connection in the wiring that links the cylinder to the boiler.

Engineer required

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

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