Display shows E21 and the refrigerator may cool poorly or not at all; compressor may run continuously.

Safety: Unplug the refrigerator before touching the compressor or electrical components.

Procedure:

• Ventilation check: Ensure adequate ventilation around the condenser and compressor. Clean dust from the condenser coil and grille.
• Listen for symptoms: After briefly restoring power, listen for repeated clicking from the compressor area (overload tripping). Unplug again.
• Inspect start device: Remove the compressor start relay/overload assembly and inspect for burn marks or melted plastic. Replace if damaged.
• Measure compressor windings (advanced): With the start device removed, measure resistance between compressor terminals. Very low or zero resistance between any two terminals may indicate a shorted compressor.
• Replace start device: If windings are within spec, fit a new Neff/Bosch-Siemens start relay/overload and test. If the compressor still fails to start and E21 persists, the compressor is likely defective and requires professional replacement.