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Samsung Oven Error Code C-21

Reviewed by the ApplianceErrors Editorial Team · Verified against manufacturer service documentation · Last verified: July 19, 2026
🛑 Critical — Stop Using 🔧🔧🔧 Advanced DIY

Oven temperature too high — sensor reads above setpoint

The most common cause of the C-21 error on a Samsung oven is cavity genuinely too hot (let it cool) (~40% of cases); start with: let the oven cool.

💰 DIY cost: $0–$380 👨‍🔧 Pro cost: $250–$550 Save $250+ by doing it yourself
Samsung Oven error code C-21 on the display panel
How the C-21 code appears on a Samsung oven display

What Does Error Code C-21 Mean on a Samsung Oven?

Oven temperature too high — sensor reads above setpoint.

C-21 fires when the cavity temperature sensor reports a reading above the setpoint or the control board's safe upper limit. The board interprets this as an overheat condition and locks out heating as a safety measure. It differs from C-20 (open or shorted sensor) because C-21 reflects a plausible but excessive temperature — pointing to either a truly hot cavity, a heating relay welded closed, or a sensor drifting low in resistance and misreporting heat.

Models affected: Samsung electric and gas ovens/ranges with electronic temperature control, including models such as NE59M4320SS, NX58R5601SS, and NE63A6511SS
What owners report: Owners commonly report this code appearing after long high-heat cooking or a self-clean cycle, where it often clears once the oven fully cools. If it returns quickly or the oven keeps climbing past the setpoint, a stuck relay is the more likely culprit and warrants stopping use until serviced.

What Causes Error Code C-21?

Here are the most common causes in order of frequency. Start with the most likely cause before moving to the next:

  1. 1
    Cavity genuinely too hot (let it cool) 40% of cases
  2. 2
    Heating relay stuck on (runaway heat) 35% of cases
  3. 3
    Temperature sensor misreading 20% of cases
  4. 4
    Control board fault 5% of cases

How to Fix Samsung Oven Error Code C-21

🔧🔧🔧 Advanced DIY Est. time: 1–3 hours
⚡ Safety first: Unplug the appliance before opening any panels or touching internal components.
  1. 1

    Let the oven cool

    Turn the oven off, unplug or switch off the breaker, and let it cool for an hour before retrying.

    ⚠️ Do not open the door during overheating; stand clear.
  2. 2

    Test the temperature sensor

    After cooling, confirm the sensor reads about 1,080 ohms at room temperature.

    🔩 Multimeter
  3. 3

    Check for a runaway relay

    If the oven keeps overheating, a stuck heating relay on the control board is likely.

    🔩 Samsung oven control board ($150–$380)
    ⚠️ An oven that overheats should not be used until repaired.

How to Reset Error Code C-21

Switch off and let the oven cool an hour. Do not use it if it keeps overheating.

Note: If the error returns after resetting, the underlying issue has not been resolved. Work through the fix steps above.

Full Samsung oven reset guide → Enter diagnostic mode →

Did this guide fix your appliance?

When to Call a Professional

A genuine overheat (stuck relay) is a safety issue — have it serviced before further use.

Average professional repair cost for this issue: $250–$550

Related Error Codes

C-20
Oven temperature sensor fault — check needed
⚠ High Severity
E-0A
Oven overheating — temperature above safe limit
🛑 Critical — Stop Using

Find Replacement Parts

Use these links to find the exact replacement parts for your Samsung Oven:

🔩
Search PartSelect
Samsung Oven repair parts
🔧
Search RepairClinic
Step-by-step video guides

External links — ApplianceErrors.com is not affiliated with these retailers.

More Samsung Oven Error Codes

E-08 Oven temperature sensor open circuit E-09 Oven temperature sensor short circuit SE Keypad/touchpad short — stuck button on control panel NF No flame detected — gas ignition failure (gas range models) E-3 Door lock motor failure — self-clean door latch issue E-43 Power relay failure on main control board

Frequently Asked Questions

Can I keep using my Samsung Oven when error C-21 appears? +
No — stop using the oven right away. C-21 is a critical temperature fault, and continuing to run it risks further damage or a safety hazard. Unplug it and resolve the fault before the next cycle.
What most commonly causes C-21 on a Samsung Oven? +
Across reported Samsung oven repairs, the most frequent is cavity genuinely too hot (let it cool) (40% of cases), heating relay stuck on (runaway heat) (35%), then temperature sensor misreading (20%). Check them in that order before replacing any parts.
C-21 keeps coming back after a reset — what should I check next? +
A reset only clears the stored C-21 fault; if it returns, the temperature problem is still present. Move on to the physical checks — let the oven cool, then test the temperature sensor — since the code will reappear until the root cause is resolved. This is an advanced repair involving deeper disassembly or electrical testing.
How much does it cost to fix Samsung Oven error C-21? +
A DIY repair typically runs $0–$380 in parts, versus $250–$550 for a professional service call, so handling it yourself saves around $250. Expect the work to take 1–3 hours.
Which Samsung Oven models show error C-21? +
C-21 is documented on Samsung electric and gas ovens/ranges with electronic temperature control, including models such as NE59M4320SS, NX58R5601SS, and NE63A6511SS. Other units sharing the same control platform can display it too, so the fixes here generally transfer across the series.

Sources & References

Content verified against manufacturer service documentation. Last verified: July 19, 2026.

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