Microwave displays F4 and will not start or stops mid-cycle.
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Disconnect power before any inspection. Do not remove the outer cabinet.
What you can do:
- Power reset: Unplug the microwave for 10 minutes, then plug it back in and test an AUTO COOK or SENSOR COOK function. If F4 appears only on sensor modes, the humidity sensor is suspect.
- Avoid steam overload: Use a microwave cover when cooking high-moisture foods. Excessive steam can temporarily affect the sensor.
- Try non-sensor modes: If manual TIME COOK works but sensor modes trigger F4, the humidity sensor or its circuit is likely faulty and needs replacement.
Service note: The humidity sensor is typically mounted in the upper cavity area behind a small grill. Replacement requires cabinet removal and exposure to high-voltage components; have a qualified technician replace the sensor and verify operation.
Repair Difficulty
Required Part
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