BoilerFaultCodesIdeal F09 L09 Fault Code
Also written as F09L09 — same fault.
The Ideal F09 L09 fault code means: your boiler's main control board has lost its programmed settings and no longer knows how to operate the specific model it is installed in.. It appears on 3 Ideal models in our database.
Technical description: Unconfigured PCB
What causes the Ideal F09 L09 fault?
This fault occurs when the boiler's central brain, the printed circuit board, suffers a memory failure or loses its identity settings. The most common reason is a sudden power surge or a component failure on the board that wipes the specific software instructions required to run your boiler safely.
This fault is often seen following summer storms, as power surges from lightning strikes can scramble the sensitive electronic memory of the boiler's control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ideal models that show the F09 L09 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal F09 L09 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026