Microwave displays E9 and will not start; interior light and display may still function.

Critical safety warning: Inverter-based microwaves operate at very high voltages and frequencies. Do not attempt to service the inverter or magnetron unless you are trained and equipped to safely discharge and test high-voltage circuits. For most users, this is a technician-only repair.

Basic user-level checks:

• 1. Power reset: Unplug the microwave for 10 minutes to reset the control. Plug back in and test. If E9 returns immediately, internal hardware is likely faulty.
• 2. Ventilation and load: Ensure the unit is not overheating and that you are using appropriate cookware and food loads. However, persistent E9 almost always indicates an internal failure.
• 3. Professional diagnosis: A technician will inspect the inverter module, magnetron, and wiring harness. Often the inverter board or magnetron must be replaced as a set on Tristar models when E9 is present.