High Lockout
F66 on Ferroli BlueHelix Pro 32C

Your boiler's main control board has detected an internal communication error, meaning it cannot process commands correctly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

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What causes this fault?

This fault occurs when the boiler's central brain, the main control board, experiences an internal electronics failure or loses the ability to talk to its sensors. The most common reason is a hardware malfunction within the PCB itself or a loose connection in the internal wiring harness that prevents data from flowing correctly.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

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