How much does it cost to fix Vaillant error code F.63?

Typical repair cost for the Vaillant F.63 fault is £280-450 including labour.

F.63 High

Vaillant F.63 Fault Code

Q: What does the Vaillant F.63 fault code mean?

Your boiler’s internal computer chip has suffered a memory error, preventing it from processing the instructions needed to run your heating.

Also written as F63 — same fault.

The Vaillant F.63 fault code means: your boiler’s internal computer chip has suffered a memory error, preventing it from processing the instructions needed to run your heating.. It appears on 53 Vaillant models in our database.

Technical description: Fault: EEPROM - EEPROM faulty

What causes the Vaillant F.63 fault?

This fault occurs when the boiler's main control board suffers a hardware failure, specifically within the chip that stores the permanent operating software. The most common reason is an electrical surge or age-related component wear that corrupts the internal memory, making it impossible for the boiler to perform its safety checks. Because the 'brain' of the appliance can no longer read its own instructions, it shuts down entirely to prevent 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.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Vaillant models that show the F.63 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant F.63 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026