F20
Zanussi Triac / Power Device Fault

Oven shows F20 and will not start, often accompanied by a clicking sound

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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

Shorted triac or power transistor on PCB, Overcurrent from a shorted heating element, PCB track damage due to arcing, Incorrect wiring after previous repair

How to Fix / Troubleshooting

Safety first: Disconnect mains power. The control board contains high-voltage components; only qualified persons should test live circuits.

Step-by-step checks:

  • 1. Inspect heating elements: Check all elements for visible damage or signs of arcing to the cavity. Test resistance to earth; any reading other than infinite indicates an insulation fault.
  • 2. Check wiring for shorts: Look for crushed or pinched wires, especially where the harness passes through metal panels.
  • 3. Inspect PCB: Remove the control board and look for a visibly blown triac or burnt tracks. If present, the board must be replaced.
  • 4. Replace faulty loads first: If an element is shorted to earth, replace it before fitting a new PCB to avoid immediate re-damage.
  • 5. Fit new control board: Install a genuine Zanussi PCB and reconnect all wiring exactly as per the original layout.

Warning: Do not continue resetting the oven if F20 reappears; this indicates a serious electrical fault.

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Repair Difficulty

Professional Required 5/5

Required Part

Main Control Board (Power Triac Section)
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