AL15
De Dietrich Thermostat / Temperature Regulation Fault

Freezer shows AL15; internal temperature appears too low (over-freezing) or too high despite setpoint.

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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 electronic thermostat function on PCB, Stuck relay controlling compressor, Incorrect sensor calibration, Shorted NTC sensor

How to Fix / Troubleshooting

Safety first: Disconnect power before accessing the control board.

  • Verify set temperature: Confirm the setpoint on the display is appropriate (e.g., -18°C). Adjust and see if the compressor behavior changes.
  • Check with a thermometer: Place an accurate freezer thermometer inside and compare actual temperature to the display. Large discrepancies suggest sensor or control issues.
  • Inspect control board: Access the main PCB and look for stuck or welded compressor relay contacts (burnt or discolored relay). If the compressor runs constantly regardless of setpoint, the relay may be stuck closed.
  • Sensor check: If previously replaced sensors are known good, the thermostat logic on the PCB is likely faulty.
  • Replace main PCB if needed: Install a new De Dietrich control board, transferring connectors one at a time to avoid errors.
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Repair Difficulty

Hard 4/5

Required Part

Main Control Board
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