- Appliances
- Microwave ovens
C21
Samsung C-21 on a microwave: internal temperature too high
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On a Samsung microwave, C-21 (or E-24) means the temperature rose over the limit during operation; Samsung describes it as fire sensed. Unplug it, wait long enough for it to cool and then restart the microwave.
Safety first
Stop and check this first
- If you see flame inside, do not open the door: switch it off, unplug it or turn off its breaker and wait for it to die out.
- Do not take the microwave's outer cover off to look for the fault: inside there is a high voltage capacitor that can hold a lethal charge even when unplugged. The magnetron, door seals and safety interlocks are for authorised service only.
Safe checks you can perform
- Smoke, flame or burning smell
- Full cool-down while unplugged
- Restart with a short, watched load
Leave these tasks to a qualified professional
- Do not attempt this professional task: Temperature sensor and circuit check
- Do not attempt this professional task: Cavity inspection after overheating
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Temperature sensor and circuit check
What they doThe authorised technician measures the temperature sensor and checks its wiring using the service manual method, after discharging high voltage as the procedure requires.
They must show youthe sensor's measured value against Samsung's value for your model.
In writingthe measured value, the conclusion and, if the sensor is replaced, its part number.
Cavity inspection after overheating
What they doIf there was smoke or flame, the technician checks the cavity, the waveguide cover and the door before declaring the unit fit for use.
They must show youthe state of the cavity and door after the inspection.
In writingwhether the unit is fit for further use and what was checked or replaced.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Smoke, flame or burning smell
- Who:
- you, without opening the door if you see flame.
- How:
- look through the glass. If there is flame or heavy smoke, keep the door closed, switch off and unplug it or turn off its breaker.
- Result that matters:
- whether there is or was fire or smoke inside.
- If there is flame or smoke:
- do not open it until it dies out and do not use it again until service has checked it.
- If no smoke or smell:
- move on to cooling.
- Evidence to keep:
- photo of the cavity and the food, and a note of what was cooking.
Evidence: Samsung Microwave Oven error codes - what do they mean?
Full cool-down while unplugged
- Who:
- you, no tools.
- How:
- unplug the microwave and wait until the casing and door feel cool. Check that the vents are not blocked.
- Result that matters:
- that the unit is cool and ventilated before restarting.
- If it was hot or vents were blocked:
- the heat explains the code; clear them before going on.
- If it was already cool and clear:
- real heat is less likely; note it for the technician.
- Evidence to keep:
- note of the waiting time and the state of the vents.
Evidence: Samsung Microwave Oven error codes - what do they mean?
Restart with a short, watched load
- Who:
- you, with a microwave-safe cup of water.
- How:
- plug in, place a microwave-safe cup of water inside and set a short time. Stay in front of it. Never run it empty.
- Result that matters:
- whether C-21 returns with a normal load and short time.
- If it does not return:
- the code came from heat during that cooking.
- If it returns with no smoke or excess heat:
- it points to the sensor or its circuit; call Samsung service.
- Evidence to keep:
- note of the time set and when the code appeared.
Evidence: Samsung Microwave Oven error codes - what do they mean? · Understanding the meaning of error codes on your Samsung microwave
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Appliances
- Brand
- Samsung
- Product type
- Microwave ovens
Known code variants
- C21
- E-24
- microondas Samsung C21 temperatura
- Samsung C-21 high temperature
- Samsung C-21 sobrecalentamiento
- Samsung microondas C-21
- Samsung microwave C-21
- Samsung microwave C21 overheat
What it means
Samsung UK defines C-21 and E-24 as microwave temperature high: during a cooking mode the temperature rose over the limit, and it adds in brackets fire sensed. Samsung Canada places C-20, C-21 and C-22 in the temperature sensor error family. It can come from real overheating (food burning, blocked vents) or from a false sensor reading. The code does not say which: seeing whether it returns after cooling, in normal use, separates them. The table is Samsung UK's microwave guide; check your model's manual to confirm the code means the same.
Warnings and stop conditions
- Higheditorial warning
If you see flame inside, do not open the door: switch it off, unplug it or turn off its breaker and wait for it to die out.
Evidence: Samsung Microwave Oven error codes - what do they mean?
- Higheditorial warning
Do not take the microwave's outer cover off to look for the fault: inside there is a high voltage capacitor that can hold a lethal charge even when unplugged. The magnetron, door seals and safety interlocks are for authorised service only.
Evidence: Samsung Microwave Oven error codes - what do they mean?
Symptoms and causes
Probable causes · in order
- Real overheating in the cavityCommon
This is Samsung's definition: temperature passed the limit and the control treats it as fire sensed. It fits if there was smoke, a burning smell or dried-out food after a long time.
Evidence: Samsung Microwave Oven error codes - what do they mean?
- False temperature sensor readingPossible
Samsung Canada groups C-21 with temperature sensor errors. If it trips with a small load and short time, with no smoke or smell, it points to the sensor or its circuit rather than real heat.
Evidence: Understanding the meaning of error codes on your Samsung microwave
- Unit still hot when restartedPossible
Samsung asks you to wait long enough for it to cool. Restarting straight away can repeat the code without a new fault.
Evidence: Samsung Microwave Oven error codes - what do they mean?
Virtual technician
Does C21 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Samsung Microwave Oven error codes - what do they mean?
Samsung · 2025 · official_doc
- 2
Understanding the meaning of error codes on your Samsung microwave
Samsung · 2026 · official_doc
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