F.64
Vaillant Internal Temperature Sensor / PCB Temperature Fault

F.64 displayed, boiler may show abnormal temperature readings or shut down unexpectedly

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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

Overheating of PCB, Faulty internal temperature sensor, Poor ventilation around boiler, PCB component failure

How to Fix / Troubleshooting

Safety: Turn off power and allow the boiler to cool.

Checks:

  • Ensure ventilation openings around the boiler are not blocked.
  • Check for external heat sources affecting the boiler casing.
  • After cooling, restore power and reset the boiler.

If F.64 persists, the PCB internal sensor or components are likely faulty and the PCB should be replaced by a qualified technician.

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Repair Difficulty

Hard 4/5

Required Part

Main Control PCB
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