How to Check a Thermistor in a Whirlpool Dryer

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If you open the door of your Whirlpool dryer and find a soggy mess instead of the warm, fluffy towels you were expecting, it may be time to check your thermistor. The thermistor helps maintain the desired temperature in the dryer tub, resulting in dry clothing at the end of a cycle. The thermistor is one of the easier, and less expensive, modules to test on your Whirlpool dryer, so it’s a good place to start troubleshooting.

Things You'll Need

  • Flat-head screwdriver
  • Bulb thermometer with a 90 to 180 F scale
  • Nut driver
  • Test leads
  • Digital multimeter
  • Remove any clothes from the dryer and clean the lint screen. Close the dryer door.

  • Press the following keys on the control panel in sequence: "Heavy Duty," "Timed Dry," "More Time" or "Less Time," "End of Cycle Signal" (Louder) and "Start" to begin a test cycle. If the dryer turns off after one minute and E1 or E2 flashes on the display, the thermistor is bad or the wiring harness is damaged. Check the wiring connections from the thermistor to the control board and replace the thermistor if the harness is undamaged.

  • Remove the exhaust hose from the back of the dryer if the test cycle operates normally. Unscrew the clamp holding the exhaust hose with a flat-head screwdriver and pull the hose off the exhaust outlet.

  • Select a temperature cycle, set the control knob to "Timed Dry," and set the drying time to 20 minutes using the "More Time "or "Less Time" buttons. Press "Start" to begin the cycle.

  • Hold the bulb of a thermometer in front of the exhaust outlet. Keep the bulb centered in the outlet, and read the temperature. Compare the temperature reading to the temperature specifications for the selected temperature cycle. If the temperature is within the specified range, the thermistor is working properly. The temperature specifications are located in the service manual, which is available online (see Resources).

  • Check the resistance of the thermistor if the exhaust temperature is outside of the specified range. Use a nut driver to remove the two hex-head screws holding the lower panel to the front of the dryer. Pull the panel off the dryer to access the thermistor.

  • Locate the thermistor on top of the exhaust duct to the right of the thermal fuse. Pull the two wires off the thermistor terminals. Connect test leads to the terminals. Connect the other ends of the test leads to the probes of a digital multimeter. Set the multimeter to the ohms scale.

  • Choose a cycle and start the dryer. Measure the exhaust temperature using the bulb thermometer. Note the temperature of the exhaust and the resistance reading on the multimeter. Compare the resistance of the thermistor to the temperature chart in the service manual. If the resistance is correct for the temperature, the thermistor is working and you should check the control board. If the resistance is not correct, you should replace the thermistor.

Tips & Warnings

  • Slow drying can be caused by a blocked exhaust hose or clogged lint trap. Check both of those before beginning more advanced troubleshooting.
  • This test involves working in and around an electrical appliance with moving parts, live current and hot surfaces. Exercise extreme caution while testing the thermistor.

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References

  • Photo Credit Ryan McVay/Lifesize/Getty Images
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