F.65
Vaillant
Electronics Overtemperature / PCB Protection Triggered
F.65 electronics fault; appliance locked out, no operation
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Severe overheating of PCB, Internal PCB fault, Short circuit on connected components, Incorrect mains voltage or surges
How to Fix / Troubleshooting
Safety: Disconnect the appliance from the mains before inspection.
- Check mains supply: Verify that the supply voltage is within Vaillant’s specified range and that there are no signs of repeated surges or brownouts.
- Inspect PCB: Look for burnt tracks, bulging capacitors, or other visible damage. If present, the PCB must be replaced.
- Check connected loads: Before fitting a new PCB, test connected components (pump, fan, gas valve) for shorts that could overload the board.
- Replace PCB: Install a new Vaillant PCB and configure any model-specific settings as per the service manual.
- Test operation: Restore power and run the appliance through several cycles to confirm stability.
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Repair Difficulty
Professional Required
5/5
Required Part
Main Control PCB
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