E4
Proline Inverter or Power Supply Board Fault (Inverter Models)

Microwave display shows E4 and unit will not start; sometimes appears after a power surge or lightning storm.

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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

Failed inverter power board, Shorted IGBT or power transistor on inverter, Damaged control PCB from surge, Loose wiring harness between control board and inverter

How to Fix / Troubleshooting

Safety first: Unplug the microwave. Inverter-based microwaves use high-frequency high voltage that is extremely dangerous. Internal repairs must be done only by qualified technicians.

User-level steps:

  • Power reset: Unplug the microwave for at least 10 minutes to allow internal capacitors to discharge and the control board to reset. Plug back in and test.
  • Check outlet: Verify the wall outlet with another appliance to ensure stable power. Avoid using long or undersized extension leads.
  • If E4 returns immediately, discontinue use and arrange service. Continued operation may cause further damage.

Technician-level actions (for reference):

  • Inspect and test the inverter power module and its components (IGBT, rectifier, filter capacitors).
  • Check the control PCB for burn marks or damaged tracks and verify low-voltage supplies.
  • Verify harness connections between the control board and inverter.
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Repair Difficulty

Professional Required 5/5

Required Part

Inverter Power Board
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