F3
Tristar
Magnetron Overcurrent / High-Voltage Fault
Microwave displays F3 and will not start; may be accompanied by fan running briefly.
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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
Shorted magnetron, Shorted high-voltage diode, Faulty high-voltage transformer, Inverter overcurrent detection (on inverter models)
How to Fix / Troubleshooting
Critical safety warning: High-voltage diagnosis should only be performed by trained technicians. Do not attempt to test the magnetron, transformer, or high-voltage diode yourself.
User-level actions:
- 1. Power reset: Unplug for 10 minutes, then plug in and test. If F3 returns immediately, internal high-voltage components are likely faulty.
- 2. Discontinue use: Do not continue trying to run the microwave, as this can cause further damage or safety hazards.
- 3. Professional service: A technician will test the magnetron, diode, transformer, and related wiring, replacing the failed component(s) as needed.
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Repair Difficulty
Professional Required
5/5
Required Part
High-Voltage Diode
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