Samsung Microwave Error C-21

⚡ Quick Answer: The Samsung Microwave error C-21 indicates an abnormal internal temperature, typically due to a malfunction in the magnetron or temperature sensor. Th... ✅ DIY Fixable

What Does Error C-21 Mean?

The Samsung Microwave error C-21 indicates an abnormal internal temperature, typically due to a malfunction in the magnetron or temperature sensor. This error often occurs during or after the heating cycle, causing the microwave to stop cooking and display the C-21 code. Unusual humming sounds may accompany this issue. To resolve, allow the unit to cool down and perform a basic reset. If the error persists, professional inspection is recommended.

Common Symptoms:

  • Error displays during or after heating cycle
  • Microwave stops cooking and shows C‑21
  • Unit may cool down before restarting

Possible Causes

  • Abnormal internal temperature detected by sensor (high)
  • Faulty temperature sensor/thermistor or its wiring (medium)

How to Fix Error C-21

DIY Fix Basic reset and cooling

  1. Disconnect microwave from power outlet
  2. Wait for at least 10–30 minutes to allow unit to cool down
  3. Reconnect power and test operation

DIY Fix Inspect for overheating triggers

  1. Ensure vents are not blocked and microwave has adequate ventilation
  2. Avoid prolonged continuous use that may overheat the appliance
  3. Check that the unit is on a stable, flat surface

Technician Only Temperature sensor/thermistor and wiring inspection

  1. Disconnect power and remove outer cabinet (technician only)
  2. Check temperature sensor/thermistor leads and connector for damage or loose wires
  3. Measure sensor resistance with multimeter to verify within expected range
  4. Replace sensor or repair wiring as needed

Parts needed: Temperature sensor/thermistor, Wiring harness/connectors

Technician Only Control board diagnostic

  1. If sensor and wiring check OK, test control board diagnostics for false high temperature reading
  2. Replace main control board if confirmed defective

Parts needed: Main control board

🛑 When to Call a Pro:
  • Error repeats after reset and cooling period
  • Unit shows signs of overheating (smoke, burning smell)
  • Temperature sensor inspection is beyond user skill level

Technical Specifications

wattage 1000W
component Magnetron
resistance 10-30 ohms
part_number DE74-20019A
voltage_rating 120V AC

Common Questions

What does C-21 error mean on Samsung Microwave?

C-21 indicates an abnormal internal temperature, often related to the magnetron or temperature sensor malfunction.

Can I fix Samsung Microwave C-21 error myself?

Yes, you can perform a basic reset and check for overheating triggers like blocked vents.

How much does it cost to fix C-21 error?

The estimated repair cost ranges from $30 to $120, including parts and labor.

When should I call a technician for C-21?

Call if the error recurs after a reset, or if you notice signs of overheating like smoke or burning smells.

Sources & References

Data last verified: 2026-01-10

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