How to diagnose a bad compressor on a refrigerator?

Diagnosing whether a residential refrigerator compressor has completely failed and needs to be replaced involves a systematic electrical and physical check. First, unplug the refrigerator and access the mechanical compartment behind the base to inspect the start relay and overload protector plugged into the compressor terminals. Second, check if the compressor housing is stone cold or dangerously overheated while interior compartments remain warm. Third, use a digital multimeter set to ohms to test for electrical continuity across the compressor terminal pins and check for ground faults against the metal casing. You can troubleshoot power delivery easily. You can verify compressor failure when multimeter tests confirm open motor windings or internal electrical shorts that prevent the motor from running.