Gas Safe: Gas work, flue work, and PCB replacement on a gas boiler must be carried out by a Gas Safe registered engineer. Homeowners can check obvious items such as heating pressure, condensate overflow, and whether a control is unplugged — then call an engineer.
Always confirm the part number against the boiler GC number and the installation manual before ordering.
Overview
F.63 is a PCB memory fault. The control cannot read its stored settings. It is almost always the electronics, not a field sensor.
Vaillant meaning: EEPROM error
Possible causes
- Defective boiler PCB (EEPROM / memory)
- Occasionally a failed display / UI that shares configuration — still treated as electronics
Possible solutions
- Reset once to rule out a glitch. Recurring F.63 means replace the PCB.
- If the display was also changed, set the DSN — see F.70. Do not replace display and PCB together without coding.
- After a new PCB, run the manufacturer start-up / gas-family procedure for that range.
Possible parts needed
- Boiler PCB for the exact GC number
- Display only if it was replaced at the same time (DSN)