Error F.63

Safety first

1) Always treat any boiler electrical/electronic faults seriously. Isolate mains power at the boiler fused spur before removing covers. Do not attempt gas valve or combustion system work unless you are Gas Safe registered. If you are unsure, stop and call a Gas Safe engineer.

2) Beware of stored charge on the PCB's power supply. There are high-voltage capacitors in the switching PSU that can hold a charge. If you are going to inspect the PCB, leave the boiler disconnected from mains for at least 10 minutes and, if you are qualified to work on electronics, check capacitor voltages with a DMM before touching the board.

Initial homeowner checks (safe, simple)

1) Record the error exactly (F.63) and any other simultaneous fault codes or symptoms (intermittent F.61/F.62, loss of display, random resets). Note when it started and any recent events (power cuts, lightning, servicing, component replacement).

2) Try a controlled reset: use the boiler reset button or isolate mains power for 10 minutes, then reapply power and observe. Some EEPROM/communication faults clear after a full power-down but persistent F.63 will reappear.

3) Check visible external connections: with power OFF, inspect plugs/wiring looms to the PCB, display module and external controls for loose connectors, corrosion or water ingress. Take photos so you can restore connectors correctly.

4) Check basic system conditions: boiler water pressure, external timer/thermostat demand, and any obvious signs of water leaks or burn marks around the boiler. If multiple unrelated faults appear, log them for the engineer.

Deeper diagnostic steps (only if you are competent with electronics; otherwise call a pro)

1) Visual PCB inspection (power OFF and isolated): remove the outer cover and visually inspect the main PCB for obvious faults — bulging, leaking or swollen electrolytic capacitors; darkened/burnt components or tracks; cracked solder joints; or corrosion from water ingress. On older ecoTEC Plus boards, failed electrolytic capacitors (commonly C5 and C9) are a well-documented cause of unstable supply rails and spurious F6n/F7n/F.63 style errors.

2) If you find swollen or leaking caps, this is a likely cause. Replacement of these capacitors often fixes intermittent electronic faults, but capacitor replacement requires correct component values, correct polarity, good soldering technique and safe handling of discharged capacitors. Typical values reported for problem caps are 470µF/35V (C5 and C9), with some people upgrading to higher capacitance/quality parts. Do not attempt this unless you have appropriate electronics experience.

3) If you have the skills and tools: with the board safely discharged and powered off, you can measure supply voltages to the microcontroller and check for unstable rails when powered. Intermittent or low 5V rail can cause EEPROM read failures. Troubleshooting electrical noise, bad regulators, or replacing caps is an electronics task — again, only for competent technicians.

4) EEPROM or firmware issues: corruption of the EEPROM may require reprogramming or a replacement PCB. Re-flashing firmware or repairing a corrupted EEPROM is specialist work and usually not feasible for a homeowner. Some engineers can repair PCBs or replace faulty EEPROM chips, but in many cases the PCB is replaced or professionally repaired.

What to do next / when to call a professional

1) If a simple reset and external visual checks do not clear the fault, stop work and contact a Gas Safe registered engineer or Vaillant-approved service. Tell them you have an F.63 EEPROM/electronics error and describe any visual findings (swollen caps, burn marks) and any intermittent related codes (F.61/F.62 etc.). Include boiler model, serial number and the history you recorded.

2) Do not attempt gas valve, combustion, or high-voltage PCB repairs yourself. PCB replacement, EEPROM reprogramming, and any work affecting safety devices must be done by a qualified engineer. If the engineer confirms PCB/component repair is possible, they can repair capacitors or replace the board safely.

3) If the unit is under warranty or a service plan, contact the installer or Vaillant service first. If you proceed to have the PCB repaired, ask the engineer for a written description of the fault, the repair performed, and any tests done so the appliance records remain complete.

Summary

F.63 is an electronics/EEPROM fault and often points to PCB/power-rail issues on older ecoTEC boilers. You can try a reset and safe visual checks, but PCB inspection, capacitor replacement, EEPROM recovery or PCB replacement are specialist tasks. For safety and compliance, call a qualified Gas Safe engineer or approved Vaillant technician for diagnosis and repair.