E12
De Dietrich Mains Supply or Internal Power Fault

Display shows power supply / low voltage error, unit may reboot intermittently

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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

Unstable mains voltage, Loose power terminal connections, Faulty internal power supply on De Dietrich PCB, Shared circuit overloaded

How to Fix / Troubleshooting

Safety first: Isolate power at the breaker before opening the electrical compartment.

Step-by-step checks:

  • Check dedicated circuit: Ensure the water heater is on a suitable dedicated circuit and that the breaker is not tripping.
  • Inspect power terminals: With power off, remove the electrical cover and verify that live, neutral, and earth connections are tight and correctly wired.
  • Eliminate extension leads: The heater should be connected directly to a fixed supply, not via extension cords.

When to call a professional: If low voltage persists or the internal power supply is suspected faulty, contact an electrician or De Dietrich technician.

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Repair Difficulty

Hard 4/5

Required Part

Main Control Board
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