F.70
Vaillant Incompatible or Unconfigured PCB

Boiler displays F.70 after PCB replacement or service

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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

Wrong PCB type fitted, PCB not coded to boiler model, Incorrect parameter settings, Communication mismatch with display unit

How to Fix / Troubleshooting

Safety: Isolate power before any PCB work.

  • Engineer-only fault: This code typically appears after PCB replacement. The PCB must be correctly coded using Vaillant diagnostic tools.
  • Contact installer: If F.70 appears after recent work, contact the installer or service engineer to reconfigure or replace the PCB with the correct model.
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Repair Difficulty

Professional Required 5/5

Required Part

Main Control PCB
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