High Lockout
F.63 on Vaillant ecoMAX

Your boiler's internal computer brain has suffered a memory error and can no longer process the data it needs to run safely.

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

EEPROM fault

What causes this fault?

This fault occurs when the boiler's main control board suffers a critical memory failure, meaning it can no longer read or store the vital settings required to operate. It is usually caused by an internal electrical component failing due to age or a sudden power surge that has corrupted the circuit board's data.

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

F.61View →F.62View →F.64View →F.65View →

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