BoilerFaultCodesAlpha d16 Fault Code
Also written as D16 — same fault.
The Alpha d16 fault code means: your boiler has detected an issue with the sensor that monitors the temperature of the gases leaving your flue, meaning it has safely shut down to prevent potential overheating.. It appears on 5 Alpha models in our database.
Technical description: Flue sensor reading
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 d16 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Alpha d16 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