F9/L9 High

Ideal F9/L9 Fault Code

Also written as F9L9 — same fault.

The Ideal F9/L9 fault code means: your boiler's main control computer is experiencing a critical error and is unable to communicate properly, meaning your heating and hot water will not work.. It appears on 1 Ideal model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: PCB FAULT
Typical repair cost £250-450 (including labour)

Engineer required

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

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Ideal models that show the F9/L9 fault code

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

Source

Ideal F9/L9 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 7 July 2026