F4
Toshiba Multiple Sensor Disagreement / Calibration Error

Freezer shows F4 and may exhibit erratic compressor cycling or incorrect temperature display.

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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

One or more thermistors out of tolerance, Poor sensor placement, Main PCB ADC calibration fault, Wiring harness cross-connection

How to Fix / Troubleshooting

Safety: Disconnect power before testing sensors.

Steps:

  • 1. Identify all sensors: Toshiba freezers typically have cabinet, evaporator, defrost, and ambient thermistors. Locate each according to the service diagram if available.
  • 2. Measure each sensor: Disconnect each thermistor and measure resistance at the same ambient temperature. Sensors of the same type should read similarly.
  • 3. Replace out-of-range sensors: Any sensor that significantly deviates from expected values should be replaced.
  • 4. Check harness routing: Ensure connectors are not swapped between sensor inputs on the PCB.
  • 5. PCB replacement: If all sensors and wiring are correct but F4 persists, the main PCB may have a calibration or ADC fault and should be replaced.
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Repair Difficulty

Hard 4/5

Required Part

Main Control PCB
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