My Thermostat Is Not Shutting Down the Refrigerator Compressor

How the Thermostat Works

• The thermostat is a small device that is located either under the floor of your freezer or by the back and side. The thermostat has a small metal coil. During the defrost cycle, the defrost heater will cause the metal to heat. This causes the metal to extend, breaking the circuit of electricity it creates. As the metal cools, it curls back sending electrical impulses that activate the compressor. If the thermostat is faulty, it will stay curled.

Accessing the Thermostat

• A thermostat located by the defrost timer is easy to access. Remove the screws from the thermostat cover to expose it. A thermostat located underneath the freezer floor requires you to first unplug the freezer and allow it to defrost. Remove the screws from the bottom panel and pull up. Some freezers have molding on the inside that might need to be removed before taking out the bottom panel. Be careful when doing this as the molding is often delicate.

Testing the Thermostat

• Pull the wires from the thermostat with a pair of pliers once the bottom panel is removed. Mark the wires with masking tape so you know which terminal they attached to. You need to test the voltage of the thermostat. A multimeter is a small device used to test voltage. Set the multimeter to the X1 setting and touch a probe to each side. If the thermostat is cooler than 40 degrees the multimeter will read zero. A warm thermostat between 40 and 90 degrees will read infinity. If the thermostat does not read either of these two, it needs to be replaced.

Other Issues

• A faulty defrost timer may cause the compressor to keep running. The defrost timer is located behind the kick plate at the bottom of the fridge. Turn the knob on the timer to see if it will advance and wait 35 minutes to see if the compressor will shut off and turn on properly. Remove the screws from the timer and pull out if it is failing to advance. Also, check the compressor coils at the back of the fridge. Dirty coils will cause the fridge to continually run.