BoilerFaultCodes.com
F.63 High Lockout

Your boiler's internal computer brain is having trouble reading its memory, causing the system to stop working for safety.

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 fault

What causes this fault?

This fault occurs when the boiler's main control board experiences a digital memory failure, meaning it can no longer access the essential instructions needed to run safely. The most common reason is a physical hardware failure within the circuitry of the Printed Circuit Board (PCB), often caused by long-term wear or an electrical surge. Because the 'brain' of the boiler can no longer verify its own settings, it shuts down the system entirely to prevent any unsafe operation.

Typical repair cost £280-450 (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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