Freezer displays AL04; interior light may work but compressor does not start.

Safety first: Unplug the freezer. Compressor and start components are connected to mains voltage.

• Listen for compressor behavior: When powered, does the compressor click on and off every few seconds without running? This often indicates a start relay or overload issue.
• Access compressor compartment: Pull the freezer away from the wall and remove the lower rear service panel. Locate the compressor and its start device (usually a plastic module clipped to the compressor terminals).
• Inspect start relay/PTC: Remove the start device and check for burnt smell, rattling pieces inside, or melted plastic. Any of these signs indicate it should be replaced.
• Check wiring and connectors: Ensure the harness from the main board to the compressor is firmly connected and not heat-damaged.
• Reassemble and test: Install a new OEM-compatible De Dietrich start device if needed, reattach the cover, plug in the freezer, and observe if the compressor now runs steadily and AL04 clears.

If the compressor still fails to start or draws very high current, the compressor itself may be seized and will require a sealed-system technician to replace.