Microwave displays H99 and will not heat; may shut down quickly after pressing Start.

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.

Possible Causes

Shorted magnetron, Shorted high-voltage wiring, Failed inverter board power transistor, Internal inverter protection trip

Warning: This error involves the high-voltage inverter system. Service should be performed only by qualified personnel.

Power cycle: Unplug for 10 minutes and retry once. If H99 returns, do not continue to operate the unit.
Check installation: Ensure the microwave is properly grounded and not sharing a circuit with other heavy loads.
Service required: A technician will typically test the magnetron for shorts and the inverter board for internal faults. Replacement of one or both components is usually required.

Professional Required 5/5

Inverter Board

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