High
F.63 on Vaillant ecoTEC exclusive System

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 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

EEPROM faulty: Electronics defective

From this model's manual
Verified against the Vaillant Ecotec Exclusive Combi installation & service manual, page 44.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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.

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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