C-21Critical Severity

Samsung Range C-21 – Oven Overtemp

Q: Why did my oven overheat during a self-clean cycle?

Self-clean cycles run the oven above 900°F to incinerate food residue. A sensor that is marginally out of spec (but hasn't fully failed) can lose accuracy at extreme temperatures, allowing the oven to exceed the self-clean thermostat cutout range. Avoid running self-clean cycles on older ovens with suspected sensor issues.

Q: My oven overheated once but seems fine now — do I still need to repair it?

Yes. A single overheating event almost certainly indicates a failing component. The sensor may be intermittently shorted, or the relay may be beginning to weld. These failures get worse. Do not use the oven until the root cause is identified.

Q: Can the oven overheat with no error code?

Yes. If the temperature sensor is shorted (reads near zero), the control board thinks the oven is very cold and applies maximum heat indefinitely — but the board may not detect this as an error until the oven trips its high-limit thermostat. An oven that smells strongly of heat or trips its breaker is overheating.

Q: Is the oven overheating error code the same as the bake element being stuck on?

Not always. The error code is triggered by the control board's temperature monitoring. A stuck relay (bake element stuck on) causes overheating, which the sensor detects and reports. A shorted sensor causes the board to apply heat based on false sensor data. Both need to be tested to identify the correct failed component.

Updated May 6, 2026

Samsung error code C-21: The oven temperature exceeded the safe maximum. The control board cuts power to the heating elements as a safety measure.

Quick Fix— 5 steps

Full guide with tools →

1
Turn off the circuit breaker immediately: Do not attempt to turn off the oven with the control panel. If the oven is overheating, go directly to the electrical panel and shut off the circuit breaker. Leave the oven door closed.
2
Allow the oven to cool completely before inspection: Wait at least 1 hour after the breaker is off before touching anything inside the oven or at the back of the range. Internal components can reach 600°F during a runaway heating event.
3
Test the temperature sensor (RTD probe): At room temp, the sensor should read ~1,080–1,100 Ω. A very low reading (shorted sensor, e.g., <100 Ω) tells the control board the oven is cold, causing it to keep heating. This is the most common cause of oven overheating.
+ 2 more steps in the full guide ↓

What Does the Samsung C-21 Error Code Mean?

The oven temperature exceeded the safe maximum. The control board cuts power to the heating elements as a safety measure.

Common Causes of the Samsung C-21 Error

1Failed control board relay (stuck closed sending continuous power)
2Shorted bake or broil element
3Failed temperature sensor
4Stuck-on safety thermostat

How to Fix the Samsung C-21 Error (Step by Step)

Turn off the circuit breaker immediately

Do not attempt to turn off the oven with the control panel. If the oven is overheating, go directly to the electrical panel and shut off the circuit breaker. Leave the oven door closed.

An overheating oven is a fire hazard. If you smell burning or see smoke, do not open the door — call 911 if appropriate.

Allow the oven to cool completely before inspection

Wait at least 1 hour after the breaker is off before touching anything inside the oven or at the back of the range. Internal components can reach 600°F during a runaway heating event.

Test the temperature sensor (RTD probe)

At room temp, the sensor should read ~1,080–1,100 Ω. A very low reading (shorted sensor, e.g., <100 Ω) tells the control board the oven is cold, causing it to keep heating. This is the most common cause of oven overheating.

Tools needed: Multimeter, Screwdriver set

Inspect the oven control board relay

If the sensor tests good, the relay on the electronic oven control board that switches the bake or broil element may be welded shut (stuck closed). This causes continuous heating even when the oven is turned off. With power off, inspect the relay for visible burn damage.

If a welded relay is suspected, do not use the oven until the board is replaced.

Tools needed: Screwdriver set

Replace the faulty component and test

Replace either the temperature sensor (if shorted) or the control board (if the relay is stuck). After replacement, set the oven to 350°F and monitor the temperature with an oven thermometer. Confirm it stabilizes within ±25°F of set.

Tools needed: Oven thermometer, Screwdriver set

When to Call a Technician

Overtemp errors are a fire risk. Power off at the breaker and call a technician before attempting any DIY fix.

Frequently Asked Questions

Why did my oven overheat during a self-clean cycle?

Self-clean cycles run the oven above 900°F to incinerate food residue. A sensor that is marginally out of spec (but hasn't fully failed) can lose accuracy at extreme temperatures, allowing the oven to exceed the self-clean thermostat cutout range. Avoid running self-clean cycles on older ovens with suspected sensor issues.

My oven overheated once but seems fine now — do I still need to repair it?

Yes. A single overheating event almost certainly indicates a failing component. The sensor may be intermittently shorted, or the relay may be beginning to weld. These failures get worse. Do not use the oven until the root cause is identified.

Can the oven overheat with no error code?

Yes. If the temperature sensor is shorted (reads near zero), the control board thinks the oven is very cold and applies maximum heat indefinitely — but the board may not detect this as an error until the oven trips its high-limit thermostat. An oven that smells strongly of heat or trips its breaker is overheating.

Is the oven overheating error code the same as the bake element being stuck on?

Not always. The error code is triggered by the control board's temperature monitoring. A stuck relay (bake element stuck on) causes overheating, which the sensor detects and reports. A shorted sensor causes the board to apply heat based on false sensor data. Both need to be tested to identify the correct failed component.

How to Fix the Samsung C-21 Error (Step by Step)

Turn off the circuit breaker immediately

Do not attempt to turn off the oven with the control panel. If the oven is overheating, go directly to the electrical panel and shut off the circuit breaker. Leave the oven door closed.

An overheating oven is a fire hazard. If you smell burning or see smoke, do not open the door — call 911 if appropriate.

Allow the oven to cool completely before inspection

Wait at least 1 hour after the breaker is off before touching anything inside the oven or at the back of the range. Internal components can reach 600°F during a runaway heating event.

Test the temperature sensor (RTD probe)

Tools needed: Multimeter, Screwdriver set

Inspect the oven control board relay

If a welded relay is suspected, do not use the oven until the board is replaced.

Tools needed: Screwdriver set

Replace the faulty component and test

Tools needed: Oven thermometer, Screwdriver set

Frequently Asked Questions

Why did my oven overheat during a self-clean cycle?

My oven overheated once but seems fine now — do I still need to repair it?

Can the oven overheat with no error code?

Is the oven overheating error code the same as the bake element being stuck on?