BoilerFaultCodes.com
F.63 High Lockout

Your boiler's internal computer brain has developed a memory error and can no longer process instructions correctly.

Call an engineer soon

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

Technical description: EEPROM faulty: Electronics defective

What causes this fault?

This fault occurs when the main control board suffers a hardware failure, specifically within the memory chip that stores the boiler's settings. It is usually caused by gradual wear of the electronic components or a sudden electrical surge that corrupts the internal software instructions. Because the boiler can no longer verify its own safety and operational data, it shuts down as a precaution.

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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Protect yourself from future repair bills

A boiler cover plan would cover faults like F.63 — no call-out fees, no surprises.

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