May 23, 2016

Diagnosing refrigerator thermistor problems video

By Sears PartsDirect staff
Diagnosing refrigerator thermistor problems.
Diagnosing refrigerator thermistor problems.

If the fresh food section of your refrigerator isn’t cooling properly, you could have a problem with the appliance’s thermistor or temperature sensor. The electronic control board monitors the thermistor and controls the refrigerator temperature based on thermistor signals. A broken thermistor could send the wrong information to the control board, resulting in a refrigerator temperature that’s too cold or not cold enough.

This Sears PartsDirect video shows how to check the thermistor to see if it’s working correctly. It also shows how to check the wires that connect the thermistor to the electronic control board to make sure the problem isn’t with the wiring or the control board. 

Check out our DIY Refrigerator Repair page for more how-to guides and videos, answers to common questions and error code charts.

Hi, this is Wayne from Sears PartsDirect. Today, we're going to talk about refrigerator thermistor troubleshooting. The thermistor senses the temperature inside the refrigerator. The electronic control board monitors the thermistor and controls refrigerator temperature based on thermistor signals. So, if your refrigerator’s not cooling, which one’s the problem?

Check thermistor for damage

Let’s check the thermistor first. For safety, unplug the refrigerator. Drop down the control box in the ceiling of the refrigerator to access the thermistor. Examine the thermistor's wire harness for damage or loose connections. If the wiring harness looks okay, let’s check the resistance of the thermistor using a multimeter.

Remove the thermistor and put the meter leads on the two white wires. The tech sheet for your refrigerator includes a temperature/resistance chart for the thermistor. You can usually find the tech sheet inside the refrigerator, stored behind the bottom front grill. Refer to this chart for the expected resistance readings for your model.

On this model, at a room temperature of 72 degrees, you should measure around 11,000 ohms of resistance through the thermistor. Place the thermistor in a cup of ice water and you should measure around 27,000 ohms of resistance because the water temperature is around 32 degrees. Replace the thermistor if the resistance readings are off by more than 10 percent. This video will show you how.

Inspect wiring harness

If the thermistor resistance checks okay, we know it’s not the thermistor. We still have 2 possible failures: the wire harness or the electronic control board. Let’s check the thermistor wiring harness. Plug the thermistor back in. Remove the 13-pin connector from the electronic control board.

Put one meter lead on the gray and black wire and the other on the red wire. You should measure the same resistance that you measured directly at the thermistor at room temperature. If the reading is different, replace the wire harness or repair the thermistor wires.

Confirm electronic control board failure

If the thermistor and the thermistor's wire harness are both working, the problem is likely in the electronic control board because we've eliminated the other possible causes of inaccurate temperature measurement. Before you buy a control board, I recommend that you make sure the compressor and evaporator fan are working.

The electronic control board operates those components based on the thermistor reading. A bad evaporator fan or failed compressor can mimic a thermistor problem. To confirm an electronic control board failure, you’ll need to turn on the compressor and evaporator fan in the diagnostic test mode.

First, reassemble the control box and then plug the refrigerator back in. Within two seconds, press the light switch 3 times and then press and hold it a 4th time until you hear a long beep. You're now in the test mode. If this doesn’t work on your model, check your tech sheet for instructions. Press the door switch twice to start the compressor. The control beeps twice and then you should hear the compressor start. To check the fan, press the door switch twice WITHIN 2 SECONDS and wait for the 2 beeps. Repeat this step two more times. The control beeps twice and then starts the evaporator fan.

If both the fan and the compressor run in the diagnostic test mode, you'll need to replace the electronic control board because we've eliminated the other possible causes of inaccurate temperature detection and control. Here's a video that shows how to replace the electronic control board.

Other possible problems

If the fan or compressor doesn't run, you can learn how to troubleshoot the evaporator fan and compressor in these videos.

Well I hope this video helps you out today. Be sure to check out our other videos here on the Sears PartsDirect YouTube Channel, and don't forget to subscribe.

Symptoms common to all refrigerators

Choose a symptom to see related refrigerator repairs.

Main causes: leaky door gasket, defrost system failure, evaporator fan not running, dirty condenser coils, condenser fan not running
Main causes: blocked air vents, compressor problems, condenser or evaporator fan not working, control system failure, sensor problems
Main causes: jammed ice cubes, broken ice maker assembly, dirty water filter, kinked water line, bad water valve, freezer not cold enough
Main causes: water valve leaking, frozen or broken defrost drain tube, overflowing drain pan, cracked water system tubing, leaking door seal
Things to do: clean condenser coils, replace the water filter, clean the interior, adjust doors to prevent air leaks, clean the drain pan
Main causes: damaged door seal, faulty defrost sensor or bi-metal thermostat, broken defrost heater, bad defrost timer or control board
Main causes: control board or cold control failure, broken compressor start relay, compressor motor failure, defrost timer problems
Main causes: blocked vents, defrost system problems, evaporator fan failure, dirty condenser coils, bad sensors, condenser fan not working

Repair guides common to all refrigerators

These step-by-step repair guides will help you safely fix what’s broken on your refrigerator.

How to replace a refrigerator temperature control board

If the temperature in your refrigerator doesn't match the temperature you set, the problem could be the temperature control board—a service technician can give you a definite diagnosis. If the board is at fault, follow these steps to replace it yourself.

Repair difficulty
Time required
 30 minutes or less
July 20, 2015
By Lyle Weischwill
How to clean refrigerator condenser coils

Help your refrigerator run more efficiently by cleaning the condenser coils. It's easy and takes just a few minutes.

Repair difficulty
Time required
 15 minutes or less
July 20, 2015
By Lyle Weischwill
How to replace a refrigerator water valve

Replace the water valve that feeds water to the ice maker and water dispenser if it no longer controls the flow of water.

Repair difficulty
Time required
 30 minutes or less

Articles and videos common to all refrigerators

Use the advice and tips in these articles and videos to get the most out of your refrigerator.

May 23, 2016

Diagnosing refrigerator thermistor problems video

By Sears PartsDirect staff

If your refrigerator isn't cooling at the right temperature, the problem could be the thermistor. Here's how to check.

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