Bosch No-Heat Condition (High Voltage System Failure)

Microwave runs but does not heat food; turntable and light operate normally, no error code displayed.

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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 magnetron, Defective high-voltage diode, Blown high-voltage capacitor, Faulty high-voltage transformer

How to Fix / Troubleshooting

Critical safety warning: Do not open the microwave cabinet. High-voltage components inside can cause severe injury or death even when unplugged.

  • Confirm symptom: Place a microwave-safe cup of water in the center of the turntable. Run on full power for 1–2 minutes. If the water remains cold and there is no steam, heating is not occurring.
  • Check power level settings: Ensure the power level is set to 100% (maximum) and that you are not in a defrost or low-power mode.
  • Listen for unusual noises: A loud humming, buzzing, or crackling sound during operation with no heat suggests a failing high-voltage component.

Next step: Because the fault is in the high-voltage system (magnetron, transformer, diode, capacitor), do not attempt DIY repair. Contact a Bosch-authorized technician for diagnosis and replacement of the defective part.

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Repair Difficulty

Professional Required 5/5

Required Part

Magnetron
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