EEPROM (Electrically Erasable Programmable Read-Only Memory) error
The F63 error code on Vaillant boilers indicates eeprom (electrically erasable programmable read-only memory) error.
Vaillant F63 means: eeprom (electrically erasable programmable read-only memory) error. The usual causes are pcb component failure (relay, capacitor, or microprocessor), power surge or lightning damage or water ingress onto the pcb. You can safely reset the boiler once — if F63 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does F63 Mean
The F63 code is shown by the boiler’s control board when it detects eeprom (electrically erasable programmable read-only memory) error. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows F63 and the boiler stops until the fault is cleared |
Common Causes
Causes documented in 18 technical sources.
| Cause |
|---|
| PCB component failure (relay, capacitor, or microprocessor) |
| power surge or lightning damage |
| water ingress onto the PCB |
| loose or corroded PCB connections |
| incompatible software version after a partial replacement |
| EEPROM data corruption |
Safety Warning
F63 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Check for visible damage on the PCB — look for burnt components, corrosion, or water marks. 2. Check all wiring connections to the PCB are secure. 3. Try a power cycle — switch the boiler off at the mains for 30 seconds, then switch back on. 4. If the fault persists after power cycling, check the error code history for related faults. 5. Verify the mains voltage supply to the PCB is stable (230V ±10%). 6. Check the earth connection
How to Fix It
Power cycle the boiler (off for 30 seconds, then on)
repair loose connections
if the PCB shows signs of water damage or burnt components, replace the PCB
ensure the replacement PCB is the correct version for the boiler model
after PCB replacement, the boiler may need recommissioning and parameter setup
Refer to the Vaillant service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
Diagnostic Tools
TroubleAtlas Score
What Is the TroubleAtlas Score?
Every boiler model is independently evaluated and scored by TroubleAtlas across 6 dimensions: reliability, efficiency, parts availability, service network, value for money, and user satisfaction. The score helps you compare models and make informed decisions when choosing a new boiler.
See All Boiler Scores →Boiler Breakdown Cover
Boiler Breakdown Cover
Protect against unexpected repair costs. Cover plans include annual service, emergency callouts within 24 hours, and full parts replacement. Compare plans side by side and choose the level of protection that fits your home and budget.
Coverage Plans — Coming SoonConsidering a New Heating System
Considering a New Heating System?
If your boiler or heat pump is over 10 years old, replacing it with a modern condensing boiler or air-source heat pump could save you up to 30% on energy bills and significantly reduce your carbon footprint.
Compare Heating System Prices →
YouTube Channel
Watch the fixes. Follow the channel.
Step-by-step boiler repair guides, equipment reviews, and heating system comparisons from qualified engineers.
New fixes every weekFix in 5
Quick fixes for common boiler faults explained in under 5 minutes
Boiler Comparator
Side-by-side comparisons of popular boiler models
Boiler Reviews
Independent reviews with TroubleAtlas Score ratings
Find a Specialist
Don’t fix it alone. Find a trusted heating engineer near you.
TroubleAtlas connects you with vetted local heating professionals who can inspect, diagnose and repair your boiler safely — no guesswork, no unnecessary call-outs.
Local heating professionals are coming to your area
We’re onboarding Gas Safe registered and licensed HVAC engineers city by city. Check back soon, or search above to see current availability.
TroubleAtlas Pro
Get cited by AI. Get found by customers.
TroubleAtlas Pro puts your business in front of homeowners searching for exactly this fault, and structures your listing so AI assistants can cite you as a trusted source.
- ✓ Appear on error code pages viewed by thousands of homeowners
- ✓ AI assistants cite your listing as a verified local specialist
- ✓ Receive direct leads with customer name and contact details
- ✓ TroubleAtlas Certified badge for your marketing materials
Affected Models
Vaillant models that can display fault code F63:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Vaillant models | — | Possible |
Frequently Asked Questions
Power cycle the boiler (off for 30 seconds, then on). According to the technical documentation, this is the first check on the list for F63.
F63 is not classified as a high-severity fault, so the boiler can be reset once. If F63 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.