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Samsung Ovens & Ranges2017–present

Error Code C-21

Oven temperature control circuit failure - may cause overheating hazard

Critical

Stop using immediately - risk of damage or safety issue

Also displayed as: C-21

What This Means

Internal temperature exceeds setpoint; Shorted sensor; Relay stuck in ON position; Heater circuit shorted

What actually causes this:

Sensor element shorted by moisture, relay contacts welded closed causing continuous heating, or control board short circuit

First Thing to Check

Turn off oven immediately and allow to cool. Check if temperature reading is normal on display

Parts Involved

Oven temperature sensorDLB relayBroil relayBake relayConvection relayMain PCB

How to Fix

  1. 1

    Disconnect power and sensor harness

  2. 2

    Measure sensor resistance (should be 1080Ω at room temperature)

  3. 3

    Check DLB, Broil, Bake, and Convection relay operation (should read ∞Ω)

  4. 4

    Check connector resistance at Main PCB CN320 (Normal 2850Ω)

  5. 5

    Check heater element resistance values

  6. 6

    Check for damaged solder joints or circuit traces

This Error Applies To

Samsung DOB30M977D Series Ovens & Ranges (2017) (2017–present)

Service manual exact match: DOB30M977D*

Related Error Codes

C-72

Steam drainage pump not removing water completely

C-30

Internal PCB thermal protection sensor not responding

C-A2

Cooling fan motor not responding to control signals

C-d1

Door lock mechanism is not responding or is stuck

C-F0

Central control PCB cannot communicate with display control board

C-F2

Touch panel cannot communicate with main control board

C-20

Temperature sensor is disconnected or failed - oven cannot measure temperature

C-70

Steam function cannot measure steam temperature

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