C-21 Critical Moderate DIY
Samsung Oven C-21 — Oven Overheating
Samsung Oven · Error code C-21
What C-21 Means
The control board read a cavity temperature above the safety threshold and shut the oven down. Treat this as a real overheat — fire risk — until proven otherwise.
Symptoms
- C-21 shown and heat shut off
- Cavity noticeably hotter than set temp
- Code triggers repeatedly after cooldown
- Sometimes follows a C-20
Common Causes
1
Failed temperature sensor reading erratically
RTD drifts and the relay stays closed too long.
2
Stuck/welded bake or broil relay on main PCB
Relay fails closed — element heats continuously.
3
Blocked oven vent
Hot air can't escape, cavity overshoots.
4
Shorted bake or broil element
Element grounds and stays energized.
5
Failed main control board
Control logic loses temperature regulation.
How to Fix It
- Stop using the oven — do not run unattended until fixed.
- Unplug/breaker off and let it cool fully.
- Confirm the oven vent (usually under rear control panel or back of cooktop) is clear.
- Measure the temperature sensor — should be ~1080 ohms at room temp; replace if off.
- Inspect bake and broil elements for blistering or arcing damage and test for short to ground.
- If relays on main PCB show burn marks or sensor and elements are good, replace the main control board.
- After repair, verify cavity temperature with an oven thermometer before normal use.
Parts You May Need
If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.
More Samsung Oven Codes
Verified against manufacturer documentation: samsung.com
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.