H99
Daewoo
Intermittent Inverter / Magnetron Protection Trip
Microwave intermittently heats and sometimes displays H99
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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
Overheating inverter, Failing magnetron drawing intermittent overcurrent, Poor inverter ground connection, Failing cooling fan
How to Fix / Troubleshooting
Safety first: Unplug the microwave before inspection. HV components are dangerous.
User-level checks:
- 1. Ensure ventilation: Confirm that all vents are clear and that the microwave has the recommended clearance around it. Overheating can trigger inverter protection.
- 2. Clean vents: Remove dust and grease from intake and exhaust vents using a vacuum and soft brush.
- 3. Avoid long continuous runs: If the error appears during long cooking cycles, try shorter intervals with rest periods to see if the issue is heat-related.
Technician-level checks:
- Verify operation of cooling fan.
- Inspect inverter and magnetron for signs of overheating.
- Check ground connections and wiring.
Recommendation: If H99 recurs after ensuring proper ventilation, schedule professional service.
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Repair Difficulty
Professional Required
5/5
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