E21
LG Dryer
Severity: ModerateWhat Does This Error Mean?
E21 means your LG dryer's exhaust temperature thermistor has detected a fault. The thermistor is a sensor that monitors the temperature of the air leaving the drum. If the sensor reads a temperature that is outside its expected range or has an open/short circuit, the dryer stops and displays E21. This is typically a sensor failure or wiring issue.
Affected Models
- DLGX5501V
- DLEX5500V
- DLE3500W
- DLGX3001P
- LG electric and gas dryers with exhaust thermistor
Common Causes
- Failed exhaust thermistor with an open or short circuit
- Loose or disconnected thermistor connector inside the dryer
- Damaged thermistor wiring caused by heat exposure over time
- Clogged exhaust vent causing exhaust temperatures to spike above the thermistor's range
- Defective main control board misreading the thermistor signal
How to Fix It
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Unplug the dryer before doing anything. For gas dryers, turn off the gas supply valve too. Wait 10 minutes to allow components to cool.
Never work inside an appliance while it is plugged in or connected to gas.
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Check the dryer exhaust vent for blockage. A severely clogged vent can cause exhaust temperatures to spike beyond the thermistor's range, triggering E21. Clean the vent before replacing any parts.
If the vent is badly clogged, clear it first and test again. The E21 may not return once airflow is restored.
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Remove the back panel of the dryer (held by screws around the perimeter). Locate the exhaust thermistor — it is clipped to the exhaust duct near the blower fan.
The thermistor is a small oval or cylindrical component with two wires attached. On LG models it is usually blue or gray.
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Test the thermistor with a multimeter set to resistance. At room temperature, a working LG exhaust thermistor should read approximately 10,000 to 50,000 ohms depending on the model. Check your service manual for the exact spec.
An open circuit (infinite resistance) or zero ohms confirms the thermistor has failed.
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Replace the thermistor if it tests out of spec. Order the part by your dryer's model number. Install the replacement, reconnect the wiring, reassemble, and run a normal cycle to confirm E21 is gone.
Thermistors clip or screw onto the duct with a small retaining clip. No special tools are needed.
When to Call a Professional
Thermistor replacement is a manageable DIY repair for most people. The part costs $15 to $35 and is usually accessible after removing the dryer's back or front panel. If you are not comfortable working inside the dryer, a technician will charge $100 to $175 for the repair.
Frequently Asked Questions
Is E21 dangerous to ignore?
Yes. The thermistor is a safety sensor. If it has failed in the short-circuit position, it may report a low temperature, causing the heater to run longer than it should. This can lead to overheating and a fire risk. Stop using the dryer until E21 is resolved.
Where exactly is the exhaust thermistor on an LG dryer?
It is clipped to the exhaust duct near the blower fan at the rear of the drum. On most LG front-load dryers, you access it by removing the back panel. It has two wires plugged into a connector and clips directly onto the metal duct.
Could a power surge cause E21?
A power surge can damage the thermistor's sensitive resistance element. If E21 appeared after a storm or power outage, the thermistor may have been damaged. An inexpensive surge protector on the dryer outlet can prevent this in the future.