Thermador
No-Heat Condition (Magnetron / HV System Failure)
Microwave runs but does not heat food; turntable, light, and fan operate normally, 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 diode,Blown high-voltage capacitor,Failed high-voltage transformer or inverter module
How to Fix / Troubleshooting
Critical safety warning: The high-voltage system in a Thermador microwave can be lethal. Do not attempt internal HV repairs unless you are a trained technician.
- Step 1 – Confirm symptom: Place a microwave-safe cup of water inside and run on high for 1–2 minutes. If the water is still cold, heating is not occurring.
- Step 2 – Check power and settings: Ensure the power level is set to 100% and that you are not in a non-heating mode (such as timer or vent fan only on OTR models).
- Step 3 – Listen during operation: A normal Thermador microwave will have a steady hum when the magnetron is active. If this sound is missing or unusually loud/buzzy, an HV component may have failed.
- Step 4 – Professional diagnosis: Internal testing of the magnetron, HV diode, capacitor, and transformer/inverter should be performed by a Thermador-authorized technician using proper safety procedures.
Note: Continuing to run a no-heat microwave can further damage components; discontinue use until repaired.
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Repair Difficulty
Professional Required
5/5
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