H21
Panasonic
Temperature Sensor / Thermistor Error
Microwave displays H21 and may stop mid-cycle, especially during sensor cooking modes.
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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
Defective cavity temperature sensor (thermistor), Loose thermistor wiring, Overheated cavity due to blocked vents
How to Fix / Troubleshooting
Safety: Avoid touching internal components behind the panels. Work only in the cavity and around external vents.
Steps:
- Allow cooling: If the unit has been used repeatedly, unplug it and let it cool for at least 30 minutes.
- Check vents: Ensure all external vents are clear of dust, grease filters are clean (for over-the-range models), and there is adequate clearance around the unit.
- Clean interior: Wipe down the interior surfaces to remove grease that can trap heat.
- Reset: Plug the unit back in and test a short manual cook cycle (not sensor mode).
If H21 reappears: The temperature sensor or its wiring is likely faulty and should be replaced by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Cavity Thermistor (Temperature Sensor)
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