Samsung Oven C-21 Error Code: Oven Got Too Hot (Overheat Safety Error)

What the code means

In Samsung's US range manuals (for example the NE59J7630 and NE63A6111 use and care guides), C-21 means the internal oven temperature rose abnormally high, as opposed to C-20, which is an open or shorted oven sensor. Samsung India's information-code page words it the same way: the temperature sensor detected a higher temperature than the set temperature, and the fix is to turn the oven off so it can cool, then set it again. Samsung's UK, New Zealand and Singapore pages simply group C-20, C-21 and C-22 together as sensor malfunctions. On the service side, the NV51CB700D wall oven service manual says the control beeps 10 times and shows C-21 when the temperature goes above the specified limit during operation, and has the technician check the oven sensor (about 1,080 ohms at room temperature), the bake, broil and convection heater resistance, whether the door lock, bake, broil and convection relays on the main board are working normally, and the sensor harness and its connector on the main board. The NV51K6650D and NV51K7770D service manuals list C-21 as a safety error with the same relay and main-board checks. So C-21 can be a real overheat (for example a relay that keeps a heater on) or a sensor or wiring fault that makes the control think the oven is too hot. Codes and wording vary by model, so check your own manual.

Likely causes

• The oven actually overheated, for example after a long high-temperature cook or broil
• Hot air not escaping properly; Samsung ties the related C-24 code to a blocked cooktop vent at the back of the range
• A faulty oven temperature sensor reading the wrong temperature
• A loose, damaged or corroded oven sensor harness or connector on the main board
• A heater relay (bake, broil, convection or door lock) on the main control board stuck closed so a heater stays on
• A failed main control board

Safe DIY checks

1. Press OFF/CLEAR (or OVEN OFF, or the Power button on newer models) to stop cooking. Leave the door closed or open it briefly to let heat out, and let the oven cool down completely.
2. Make sure nothing is covering the oven vent at the back of the cooktop, such as a pan, foil or a baking sheet. Samsung says a blocked vent makes the oven temperature rise faster than normal (its C-24 code).
3. Once cool, turn the oven back on and set it again. Samsung India's fix for C-21 is exactly this: let it cool, then try the setting again.
4. If C-21 returns, turn the range off at the circuit breaker (or unplug it), wait at least 30 seconds, then restore power. This is the step in Samsung's own manuals and US error code guide.
5. If the oven keeps heating after you turn it off, or the code returns after the power reset, turn the breaker off and leave it off. Don't keep using the oven; request service.
6. Write down your full model number from the label before calling, since Samsung notes the codes differ by model.

Parts that commonly fix it

Always match the part number to your exact model.

Related codes

• C-F2 Samsung Oven C-F2
• SE Samsung Oven SE
• F11 Frigidaire Oven F11
• F2 GE Oven F2
• F97 GE Oven F97
• F3E1 KitchenAid Oven F3E1

All Samsung codes →

Sources

1. Samsung NE59J7630 series range user manual, Information codes (C-21: internal temperature rises abnormally high; OVEN OFF, then power off 30 seconds, then call for service; via ManualsLib)
2. Samsung NE63A6111 electric range use and care guide (C-20/C-21/C-30 group; OFF/CLEAR, 30-second power disconnect, call for service; ShopAppliances copy)
3. Samsung India: Information codes on my oven (C-21: sensor detects higher than set temperature; turn off to cool and try again)
4. Samsung UK: Information codes on my oven (C-20, C-21, C-22 sensor malfunctions; power off 30 seconds)
5. Samsung US: Range or wall oven error codes (C-24 blocked vent; reset steps for other codes)
6. Samsung NV51CB700D wall oven service manual, failure codes (C-21 after 10 beeps; sensor 1,080 ohms, heater, relay and harness checks; via ManualsLib)
7. Samsung NV51K7770D series service manual (C-21 safety error; relay and main PCB checks; via ManualsLib)