d9 Low

Alpha d9 Fault Code

Also written as D9 — same fault.

The Alpha d9 fault code means: your boiler is displaying a stored history of previous errors rather than an active fault, allowing you to review the last five issues it experienced.. It appears on 9 Alpha models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Fault history - by rotating the CH knob (item 6 in Fig. 18) in this menu the last five faults will be displayed

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 d9 fault code

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

Source

Alpha d9 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