High Lockout
F.63 on Vaillant ecoTEC

Your boiler's internal computer brain has developed a memory error and can no longer process the information 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 error | Electronics defective

What causes this fault?

This fault occurs when the main control board suffers a permanent memory failure, meaning it can no longer remember the specific settings required to run your boiler safely. The most common reason is a physical hardware defect within the internal circuitry, often caused by age or an electrical surge that has damaged the board’s microchips.

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 →F.67View →

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