Measure the resistance between the two white wires as shown in this document.

Use a multimeter set to the ohms (Ω) setting.

Gently put the probes into the connector holes that correspond to the white wires. Alternatively, you can use sharp insulation piercing probes on the white wires.

Measure the resistance of the thermistor.

If the measurement is neither open (OL) nor shorted (less than 1Ω), measure the temperature in the fresh food compartment. Compare these figures to this chart. If it isn't in spec, go to the next step.

The resistance of the thermistor should be about 11kΩ at room temperature.