F10
Saunier Duval Low or unstable mains voltage / power supply fault

F10 error, water heater does not start, often after power issues

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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

Mains voltage below specification, Loose power connections, Internal power supply fault on PCB, Neutral/earth wiring issue

How to Fix / Troubleshooting

Safety first: Turn off the appliance before inspecting electrical connections. Only qualified persons should work on mains wiring.

Steps:

  • Check supply: Verify that the heater is connected to a stable 230 V AC supply (or local standard). Avoid using long extension leads.
  • Inspect terminal block: Remove the electrical cover and check that live, neutral, and earth are securely connected and not overheated.
  • Test outlet: Plug another appliance into the same outlet to confirm proper operation. If voltage is low or fluctuating, contact an electrician.
  • PCB power supply: If external supply is good, the internal low-voltage power supply on the PCB may be defective and the board will need replacement.

Warning: Never work on live circuits. If you are not trained, call a professional.

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Repair Difficulty

Hard 4/5

Required Part

Main Control PCB
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