Refrigerator shows E05 and may not cool; compressor does not start or starts briefly then stops.

Critical safety: This fault involves high-voltage and compressor circuits. Disconnect power before inspection. Do not attempt sealed system repairs without proper training and tools.

Basic checks:

• 1. Power cycle: Unplug the unit for 10 minutes, then restore power. Listen for the compressor starting (a low humming sound). If E05 returns and the compressor remains off, continue.
• 2. Inspect rear electronics area: Pull the refrigerator away from the wall. Remove the lower rear cover to access the compressor and inverter module (if equipped). Ensure the area is clean and well ventilated.
• 3. Check wiring connections: With power disconnected, inspect the harness between the main control board and the inverter/compressor. Look for loose plugs, burnt connectors, or damaged wires. Reseat all connectors firmly.
• 4. Visual inspection of inverter: Look for burn marks, melted plastic, or a burnt smell from the inverter module. Any such signs indicate the module should be replaced.
• 5. Compressor test (advanced): With power off and inverter disconnected, measure resistance between compressor terminals. Values should be balanced and not shorted to ground. Abnormal readings indicate a failed compressor, which requires professional replacement.
• 6. Replace suspected module: If wiring and compressor test good, replace the compressor inverter module with the correct Gaggenau/Bosch part. Mount it securely and reconnect all harnesses.

Professional service strongly recommended: Because this error involves high-voltage and sealed system components, most homeowners should contact an authorized Gaggenau technician for diagnosis and repair.