Overview
F.63 on a Vaillant Turbomax Plus 824/828E indicates an EEPROM error — an electronic fault where the boiler’s non-volatile memory (EEPROM) is reporting corruption, failure or loss of stored configuration data. The EEPROM lives on the main PCB (printed circuit board) and stores settings and calibration data required for normal operation. When the control electronics cannot read or validate that memory the boiler will lock out and display an F.63 to prevent unsafe or unpredictable operation. Severity: moderate to high. This is not a simple sensor or plumbing fault; it affects the boiler’s control electronics and will typically prevent reliable operation until fixed. In many cases the fault is caused by a failing PCB, a corrupted firmware/memory chip, a bad connection, or a power surge. Because it involves gas appliance electronics and safety-critical control, this fault is not a routine DIY repair and should be diagnosed and repaired by a Gas Safe registered engineer or an authorised Vaillant service technician. Short simple checks by a homeowner are possible, but replacement or internal PCB repairs should be done professionally.
Possible Cause: EEPROM (Electrically Erasable Programmable Read-Only Memory) error
Troubleshooting Steps
Safety first: before you touch anything, switch off the boiler at the mains (isolate power) and turn off the gas supply if you will be opening the case. Do not run the boiler if it keeps tripping to F.63 — leave it powered down until inspected by a qualified engineer. If you smell gas or suspect a gas leak, evacuate, ventilate and call the gas emergency number immediately.
Initial homeowner checks (safe, simple):
1) Try a single reset: use the boiler reset button or switch the boiler off at the mains for 60 seconds, then power up and see if the fault returns. Do not keep repeatedly resetting — repeated resets are not recommended and won’t fix a persistent EEPROM fault.
2) Check mains power stability: look for recent power cuts or surges at the times the fault started. If you have a fuse box trip or other appliance issues, mention that to the engineer.
3) Note related behaviour and other error codes: record whether other F-codes (F.61, F.62, F.64 etc.) appeared earlier, how often the code occurs, whether it happens after power loss, and whether heating or hot water demands were running when it happened. Take a photo of the display and any LED indicators.
4) Visual external check: with the boiler isolated from mains, inspect the visible wiring/conduit to the boiler for obvious damage, water ingress, or corrosion. Don’t probe live electronics.
Further diagnostic steps for a qualified engineer (do not attempt unless qualified):
1) Confirm fault memory: the engineer will read the service menu and confirm the F.63 EEPROM fault and any associated logs.
2) Power supply and earth checks: verify correct mains voltages and earth/neutral integrity, check for signs of voltage spikes that can corrupt EEPROM.
3) Inspect the PCB: remove the cover and inspect the main PCB for burned components, bulging capacitors, water damage, corrosion or loose connectors. Reseat all board connectors and ribbon cables to ensure solid contact.
4) Check board fuses and replace only with specified type/rating if blown.
5) Test other components and communications: confirm eBUS/communications to other modules, check gas valve wiring and ignition components if the fault history overlaps F.61–F.64 codes.
6) EEPROM/firmware action: if the EEPROM is corrupt the options are reflash (where supported by manufacturer tools), replace the PCB, or replace the affected memory chip. Vaillant-authorised service engineers will follow the manufacturer procedure — many independent engineers will replace the PCB assembly.
7) After repair, run full functional and safety checks including combustion, gas pressure, electrical safety and system operation.
When to call a professional: call a Gas Safe registered Vaillant engineer as soon as possible if the F.63 persists after a safe power-cycle or if the code returns repeatedly. Because the fault is electronic and affects control logic, professional diagnosis and repair are required. Provide the engineer with the error history, photos and any notes about recent power events.
Additional notes: do not attempt internal PCB repairs unless you are qualified and authorised — incorrect work can create safety and carbon monoxide risks. Resetting once for a test is acceptable, but avoid repeated resets. Document times and frequency of fault occurrences to help the engineer diagnose intermittent issues.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Vaillant Turbomax Plus 824/828E.