F66 High

Ferroli F66 Fault Code

The Ferroli F66 fault code means: your boiler's main internal computer has developed a technical fault and can no longer control the heating system safely.. It appears on 5 Ferroli models 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: Controller ABM03B error – controller internal error

What causes the Ferroli F66 fault?

This fault occurs when the boiler's internal computer chips suffer a hardware failure or a memory corruption, meaning the board can no longer process safety data correctly. The most common reason is electrical degradation of the circuitry over time or a sudden power surge that damages the sensitive components on the PCB.

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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Ferroli models that show the F66 fault code

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

Source

Ferroli F66 fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026