Hitachi Overcooling – Thermostat or Sensor Miscontrol

Freezer over-freezing, food is excessively hard and ice forms on packaging

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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

Faulty freezer thermistor, Stuck relay on main control PCB, Incorrect temperature setting, Failed mechanical thermostat (on basic models)

How to Fix / Troubleshooting

Safety first: Disconnect power before accessing controls or sensors.

  • Verify temperature setting: Adjust to a moderate setting (around -18°C) and allow 24 hours to stabilize.
  • Test thermistor or thermostat: For electronic models, measure thermistor resistance and replace if out of spec. For mechanical thermostats, check for continuity; a thermostat stuck closed will overcool.
  • Inspect main control PCB: Look for a stuck compressor relay that remains engaged even when the set temperature is reached.
  • Replace faulty component: Install a new Hitachi thermistor, thermostat, or main control PCB as indicated by testing.
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Repair Difficulty

Medium 3/5

Required Part

Thermostat / Freezer Thermistor
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