To locate the relay switch, slide the refrigerator out until you can reach the back of the unit, and remove the access panel. Follow the wiring from the compressor to a metal terminal box. Take the cover off this box to reach the relay switch.
The relay switch receives the electrical signal from the thermostat that prompts it to turn the compressor on. When the temperature goes to high inside the unit, and the refrigerator starts to make a clicking noise near the bottom of the unit, a failure in this switch is a possible cause. Listening to the relay while jiggling it for rattling sounds diagnoses inner damage that may require replacement. Multimeter testing analyzes proper electrical performance.