Siemens No Heating – High-Voltage System Failure

Microwave runs (light on, turntable rotates, fan noise present) but food remains cold.

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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 transformer or inverter, faulty high-voltage diode, open high-voltage capacitor

How to Fix / Troubleshooting

Critical safety warning: The high-voltage section of a microwave is extremely dangerous. Do not remove the outer cabinet or attempt to test HV components unless you are a trained technician.

User-level checks:

  • 1. Verify load: Always test heating with a cup of water. Never run the microwave empty.
  • 2. Check power level: Ensure the power level is set to 100% (or maximum) and not to a low setting.
  • 3. Try different modes: Test both microwave-only and combination modes (if available). If none heat, the HV system is likely faulty.
  • 4. Power reset: Unplug for 5 minutes, reconnect, and test again.

If the unit still does not heat, internal components such as the magnetron, transformer/inverter, diode, or capacitor must be tested and replaced by a Siemens-authorized technician.

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Repair Difficulty

Professional Required 5/5

Required Part

Magnetron
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