Lawn Equipment Parts
How To Fix A Dryer That's Too Hot
Click a Part Below to Start Your Repair:Cycling Thermostat High Limit Thermostat Thermistor Exhaust Vent
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The cycling thermostat in your dryer monitors the temperature in the blower housing and cycles the heating element or gas burner on and off as required to maintain the proper temperature. If the thermostat becomes defective or cannot accurately sense the airflow temperature, the heater or gas burner may stay on too long and create an unsafe temperature in the drum. The cycling thermostat has normally closed contacts that open on temperature rise and therefore testing for continuity will not easily determine if the thermostat is defective. You should first inspect the exhaust vent, blower wheel, drum seals and drive motor to verify that you have proper airflow before replacing the cycling thermostat.
How to test dryer’s cycling thermostat using a multi-meter:
- After ensuring you have unplugged your dryer, open your dryer’s cabinet to locate your cycling thermostat. It will be found along the flow of air from the drum, often attached to the blower housing.
- In order to test it, gently remove the cycling thermostat from the dryer.
- To test for continuity, set your multi-meter to Rx1 and place the prongs on the thermostat’s terminals. You should see a reading of zero or infinity.
- If your test produces any other reading, you need a replacement cycling thermostat.
High Limit Thermostat
The high limit or safety thermostat is used to protect the appliance from overheating due to a restricted airflow condition. This thermostat is normally located above the heat source and is designed to activate only when the air flow is reduced enough to allow the heat to rise and trip the thermostat, removing power to the element or gas burner. The thermostat is not designed to trip repeatedly and when this condition happens, the contacts inside may fuse together and no longer provide safety protection. This can allow the burner or element to stay on too long and the temperature may rise to an unsafe level. The high limit thermostat has normally closed contacts that open on temperature rise and therefore testing for continuity will not easily determine if the thermostat is defective. Verify that the exhaust vent is clear and not restricted and that the blower wheel and motor are operating properly before replacing the high limit thermostat. Remove power from the appliance before attempting this repair.
How to test a dryer high limit thermostat with a multi-meter:
- Disconnect your dryer from the power source and open your dryer’s cabinet.
- After locating the high limit thermostat, carefully remove it from the dryer in order to test it. It will be located somewhere in the path of air leaving the drum, often on the inside of the exhaust system or on the blower wheel housing.
- Set your multi-meter to the Rx1 setting and touch the terminals with the probes to test for continuity.
- If your test results in a reading other than zero, you need a replacement high limit thermostat.
Some newer models of electronic control dryers may use a thermistor in place of a cycling thermostat, to regulate the temperature in the dryer drum. The thermistor senses the airflow temperature as it exits the drum. The thermistor is a solid-state device and will vary in resistance according to the temperature. This resistance is monitored by the electronic control board which operates a relay controlling the heater or burner. If the thermistor becomes insulated with lint or foreign matter or is damaged or otherwise defective, it will not register the proper resistance and the control board may not turn the heater or burner off at the proper temperature. Some models may display a fault code when this happens. If your dryer is displaying a fault code, you can refer to our list of common appliance fault codes to determine the source. You can test the thermistor with a multi-meter if you know what the resistance should be at room temperature. This information may be located on the schematic diagram for the dryer.
How to test a dryer thermistor a multi-meter:
- Unplug your dryer and open the dryer’s cabinet.
- Locate and gently remove the thermistor to test it, it is normally located on the blower housing. Allow the thermistor to rest outside of the dryer prior to testing as it needs to be at room temperature to produce a reliable reading.
- Set your multi-meter to the Rx1 setting and place the prongs on each of the thermistor’s terminals.
- If the reading does not match what the resistance should be at room temperature, which varies by model, you need a replacement thermistor.
If your clothes dryer appears to be too hot on top of the cabinet, the problem may be with the exhaust vent. If the vent becomes restricted, air flow will be reduced, and the temperature inside may rise causing the cabinet top to be hotter than normal. This normally results in the high limit safety thermostat tripping and the clothes will take longer to dry. This is a safety concern and the exhaust vent should be checked regularly and cleaned when required.
How to check and clean a dryer’s exhaust vent:
- Disconnect your dryer from the power source as well as the vent hose.
- If possible, remove the ducts for easier cleaning.
- Use a vent cleaning brush to clean the inside of the ducts and any vent covers. Insert the brush into the ducts and ensure you only spin it counterclockwise, as turning it clockwise could unscrew the segments.
- You may need to do this from both the inside and outside, depending on how long your ductwork and brush are.
- If you are unable to clean the duct work with a brush, you may need replacement ductwork and/or vents.
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