Microwave displays 'H99' and does not heat; may show error immediately on 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, Inverter board overcurrent protection trip, Shorted HV wiring, Faulty main PCB control to inverter

Safety: Unplug the microwave. High-voltage troubleshooting is not a DIY task.

Reset: After unplugging for 10–15 minutes, reconnect and test. If H99 returns, internal HV components are likely shorted.
Professional diagnosis: A technician should check the magnetron for shorts, inspect HV wiring, and test the inverter board. Replacement of the magnetron and/or inverter is usually required.

Professional Required 5/5

Magnetron / Inverter Board

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