Thermistors, Thermostats, Thermal Fuses, Thermal Cutoffs… with so many parts monitoring the temperature of your dryer it can get a little confusing. Although they may all sound similar, each part serves a different purpose, working to make sure that your dryer is running safely and efficiently.
In this Product Pick of the Week, we’ll be talking about some of the most common temperature sensing and monitoring parts in your Dryer and share with you a few signs that they may need to be replaced.
A Thermistor, also called a Thermal Resistor, is used to monitor the air temperature in the dryer drum by signaling to the control board.
How it works: As the temperature of the dryer increases, the resistance in the Thermistor decreases, and vice versa. Once the resistance reaches the point where the temperature is high enough to dry the clothes, it signals to the control panel to shut off the heater. As the temperature drops and the resistance increases again, the control panel is signaled when the heater needs to be turned back on to maintain the proper drying temperature.
Signs this part may need to be replaced: A dryer with low/no heat or an “Error” message. If the part has been tested and the resistance is lower than recommended or does not adjust as the temperature changes it needs to be replaced.
Much like a Thermistor, the Thermostat also monitors the temperature inside of the dryer. Most dryers will have a preset thermostat with a specific set temperature allowance. These can come in the form of probe, disc, or surface thermostats.
How it works: Dryer Thermostats are typically bi-metal, meaning that they open and close as the temperature of the dryer changes. The bi-metal in the thermostat will bend at a certain set temperature, breaking the circuit and contact to the heating element. As the dryer cools, the bi-metal will return to its original shape and re-connect the circuit. The different types of thermostats monitor different temperature ranges or different elements of the dryer.
Hi-Limit Thermostats: This part cycles the burner or heater off if the dryer exceeds the normal temperature range to protect it from overheating and can usually be found on or near the heating element.
Cycling Thermostats: This part works in much the same way, cycling the heater or burner on and off to maintain the target temperature (operating temperature). This temperature will vary by model and is typically noted on the part itself.
Signs this part may need to be replaced: A dryer with low or no heat. Test the part for continuity.
The Thermal Fuse acts as a safety devices for the dryer.
How it works: When the temperature reaches a dangerous level, the Thermal Fuse blows, completely cutting off power to the heater. Unlike a Thermistor or Thermostat, this part cannot be reset or repair, and instead must be replaced each time this happens.
Signs this part may need to be replaced: A dryer that will not start. This part typically needs to be replaced if the cycling thermostat has malfunctioned or the ducting has become clogged. Test the part for continuity.
The Thermal Cutoff is very similar to a Thermal Fuse. This set of two thermostats breaks contact when the dryer reaches an unsafe temperature to prevent it from overheating. The pair cannot be repaired if this happens and needs to be replaced.
Signs this part may need to be replaced: A dryer that will not start. This part typically needs to be replaced if the ducting is clogged. Test the parts for continuity.
As you may have noticed, the only way to be sure if any of these parts need to be replaced is to test them for continuity. You can find instructions on how to do this here: Does This Part Work? | Using a Multimeter to Test for Continuity. You can also find dryer repair guides & more here: Dryer Help & Tips and any parts you may need on our website.
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Written by: Sarah Walker