H42
Panasonic Steam / Humidity Sensor Circuit Fault

Microwave shows H42 and sensor cooking functions do not operate correctly.

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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

Open or shorted humidity sensor, Loose sensor connector on control PCB, Failed control PCB sensor input

How to Fix / Troubleshooting

Safety: Do not remove the outer cover. Work only inside the cooking cavity.

What to do:

  • Unplug and reset: Disconnect power for 5–10 minutes, then reconnect.
  • Clean sensor area: Thoroughly clean the interior ceiling and side walls, especially near any small vents or grills where the sensor is located. Grease buildup can affect readings.
  • Avoid steam-heavy tests: After cleaning, test with a simple sensor reheat using a small portion of food, not a large pot of boiling water.

If H42 persists: The humidity sensor or control board likely needs replacement. Contact a qualified technician.

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Repair Difficulty

Medium 3/5

Required Part

Humidity Sensor
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