Samsung Microwave Error Code E-21 — Temperature Sensor Fault
What this means
The E-21 error code indicates the Samsung microwave's cavity or magnetron temperature sensor is reading outside its expected range. This sensor helps the microwave regulate cooking power and prevent overheating. A faulty sensor can cause the microwave to shut down prematurely, cook unevenly, or refuse to start.
Alternate codes: E21
Step-by-step fix
4 stepsPower cycle the microwave
Unplug the microwave for five minutes and plug it back in. Run a one-minute test by heating a cup of water. If the error clears, a temporary glitch may have been the cause.
If the microwave feels unusually hot to the touch on the outside, let it cool for 30 minutes before testing.
Locate the temperature sensor
Unplug the microwave. Remove the outer case by unscrewing the cabinet screws. The temperature sensor is typically a small thermistor mounted near the top of the cavity or on the magnetron housing. It connects to the control board via a two-wire harness.
WARNING: The high-voltage capacitor inside the microwave can hold a lethal charge even when unplugged. Do not touch any high-voltage components.
Test the sensor with a multimeter
Disconnect the sensor wires and measure resistance. At room temperature, Samsung microwave thermistors typically read 5,000–10,000 ohms (varies by model — check the tech sheet). OL or 0 ohms indicates a failed sensor.
The exact expected resistance depends on your model. Look for a tech sheet inside the microwave cabinet or search your model number online.
Replace the temperature sensor
If the sensor reads out of range, remove the mounting clip or screw, disconnect the wires, and install the new sensor. Reassemble the case and test.
Route the sensor wires away from the magnetron and high-voltage transformer to avoid interference.
When to call a professional
Given the hazardous high-voltage components inside a microwave, if you're not comfortable identifying and avoiding them, have a technician handle the sensor replacement.
Related error codes
Information compiled from manufacturer service manuals, official troubleshooting documentation, and appliance repair industry resources. This guide is for informational purposes only — always consult a qualified technician for complex repairs.
Learn more about our sourcesParts you may need
Temperature Sensor / Thermistor
Part #DE32-10013A · $10–$25
If sensor reads outside the expected resistance range
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