Samsung · Oven Critical
C-21 — Oven Overheating
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.
- Keep using it?
- No — service first
- DIY difficulty
- Moderate
- Verified against
- samsung.com ↗
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.
Why it happens
Typical signs: C-21 shown and heat shut off · Cavity noticeably hotter than set temp · Code triggers repeatedly after cooldown · Sometimes follows a C-20
- Failed temperature sensor reading erratically RTD drifts and the relay stays closed too long.
- Stuck/welded bake or broil relay on main PCB Relay fails closed — element heats continuously.
- Blocked oven vent Hot air can't escape, cavity overshoots.
- Shorted bake or broil element Element grounds and stays energized.
- Failed main control board Control logic loses temperature regulation.
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
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: samsung.com.