E12 Medium

Alpha E12 Fault Code

The Alpha E12 fault code means: your boiler has lost the signal from the sensor that monitors the temperature of your hot water cylinder, meaning it may struggle to heat your stored hot water correctly.. It appears on 4 Alpha 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: Cylinder sensor fault
Typical repair cost £120-220 (including labour)

Engineer required

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

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Alpha models that show the E12 fault code

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

Source

Alpha E12 fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026