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Samsung Air Conditioner E121 Error Code
Room temperature sensor fault on Samsung air conditioners.
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The room air sensor at the indoor unit has an open or short circuit, or isn't plugged in properly. Samsung says that when this alarm shows and the unit won't switch on, a shorted or failed room sensor is the likely cause.
Compatible models
Samsung wall units including WindFree wall units in the AR**TSF series, the AC018/AC024 MNADCH high-wall units and DVM WindFree wall units (AM***TNVD); Samsung's regional pages show it as E1/C1 then 21.
Also shown as
No other codes are listed for this fault.
Difficulty
Try the basic checks, but the usual fix is a technician's job.
Not sure you are reading the code right? See how to read Samsung air conditioner codes.
How to fix Samsung E121
Try a power reset
Switch the breaker off for about five minutes and restart. If the unit then runs normally, note the date in case it comes back.
Record the full code
If it returns, write down both parts of the display (E1 then 21, for example) along with the model number.
When to call a technician
A sensor fault needs a technician to test and replace the thermistor. Samsung lists this as a code for an authorized service center.
Parts linked to E121
These are the parts most often behind this code. Tap one to see what it does and the signs it is failing.
Order parts by your full model number so they fit.
Frequently asked questions
Which Samsung models show the E121 code?
Samsung wall units including WindFree wall units in the AR**TSF series, the AC018/AC024 MNADCH high-wall units and DVM WindFree wall units (AM***TNVD); Samsung's regional pages show it as E1/C1 then 21.
Can I fix Samsung E121 myself?
Only the basic checks. You can safely try the steps above, but E121 usually points to a part or fault that needs a technician.
Other Samsung air conditioner codes
- CFFilter cleaning reminder
- ClAuto Clean running
- dFDefrosting the outdoor unit
- E101Indoor and outdoor units aren't communicating
- E122 / E123Indoor coil temperature sensor fault
- E154Indoor fan error
- E162 / E163Control board memory error
- E153 / E665Drain pump or float switch problem
- E554Refrigerant leak or low refrigerant
- E422Refrigerant flow blocked
- E458Outdoor fan error
- E416Compressor running too hot
- E221 / E231 / E251Outdoor temperature sensor fault
- E461 / E464Compressor or inverter fault
- E466Power supply voltage problem
- E440 / E441Outside temperature beyond operating limit
Last reviewed 2026-10-19. Codes and steps can vary by model; check your owner's manual.