Back Button

How to Test a Freezer Thermistor

Megan Mattingly-Arthur

Refrigerator freezer compartments use an internal temperature sensor known as a thermistor to regulate the compressor and evaporator fan. If there's a problem with the thermistor, the freezer may be too cold or too warm, or the compressor fan may cycle on and off more than usual. Before you go to the trouble of replacing the thermistor, you can test it with a multimeter to ensure that it's the source of the problem.

Use a multimeter to test your freezer's thermistor.

Step 1

Unplug the refrigerator from the wall outlet to avoid electrical injury while testing the freezer thermistor.

Step 2

Remove the contents of the freezer, including the shelves. If your freezer is equipped with an automatic ice maker, take out the ice bucket and remove the screws securing the ice maker to the back or side of the freezer compartment. Detach the connected wiring and remove the ice maker. Remove the ice maker mounting bracket as well.

Step 3

Remove the appropriate freezer panel to access the thermistor; this is usually the back panel in side-by-side models or the floor in freezer-on-top models. Note that the access panels may be held in place by screws or retaining tabs; remove the screws or use a flat-head screwdriver to lift the retaining tabs. Set the removed freezer panel aside.

Step 4

Find the thermistor near the freezer's control board. Look for a thin plastic component with two wires attached to it. Disconnect the thermistor wires from the control board wiring harness; pull the slip-on wiring connectors with a pair of needle-nose pliers to detach them.

Step 5

Switch on the multimeter and set it to RX1 to read resistance. Touch the multimeter probes to the ends of the thermistor wires. Compare the multimeter readings to the ones listed on the tech sheet that came with your refrigerator. Desired readings vary drastically by brand and model; consulting the tech sheet is the surest way to determine whether the thermistor is functioning correctly.