H3
Midea Power Supply Overheat / Transformer Protection

Microwave shows H3; unit may shut down mid-cycle and then restart after cooling.

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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

Overheating high-voltage transformer, Blocked airflow around transformer, Overloaded cooking cycles, Failing transformer drawing excess current

How to Fix / Troubleshooting

Safety warning: Unplug the microwave. High-voltage transformer work is for professionals only.

User-level actions:

  • 1. Reduce load: Avoid running the microwave at maximum power for extended periods. Use lower power settings for long cooking tasks.
  • 2. Improve ventilation: Ensure the unit has proper clearance and that vents are clean.
  • 3. Allow cooling: If H3 appears, let the unit cool fully before reuse.

Technician-level actions:

  • Inspect transformer for signs of overheating (discoloration, odor).
  • Verify cooling fan operation and airflow.
  • Measure transformer current draw under load.
  • Replace transformer or related components if overheating persists.
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Repair Difficulty

Professional Required 5/5

Required Part

High-Voltage Transformer for Midea Microwave
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