What E221 means
The outdoor temperature sensor tells the control board how hot or cold it is outside, so it can adjust compressor speed and defrost cycles. A faulty sensor triggers E221 and the unit may stop or run inefficiently.
Samsung AC E221 Error — Outdoor Temperature Sensor Fault & Fix
E221
Quick answer
E221 means the outdoor ambient temperature sensor has an open or short circuit. The outdoor unit cannot measure outside air temperature.
What does the E221 code mean?
E221 is an outdoor ambient air temperature sensor error. The thermistor is reading open-circuit or short-circuit.
Common causes
- Defective outdoor temperature thermistor
- Loose connector on the outdoor PCB
- Wiring damage (UV degradation, rodent damage)
- Outdoor PCB fault (rare)
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How to fix the E221 error
Power off
Isolate at the breaker.
Locate the sensor
On the outdoor unit, the ambient sensor is usually mounted near the condenser coil air intake, connected to the outdoor PCB.
Check the connector
Unplug and reseat.
Measure resistance
At 25°C, expect around 10 kΩ. Replace if reading is open or zero.
Replace
Swap the thermistor and route the wire away from hot components.
Safety first: The outdoor unit has high-voltage components and a running compressor. Always isolate power and wait for the compressor to stop before opening.
Part you may need: Outdoor ambient temperature sensor (NTC thermistor)
Outdoor sensors are exposed to weather. Use the correct weatherproof replacement.
Frequently asked questions
Will the AC still cool without this sensor?
It may run but inefficiently, and defrost cycles will not work correctly in heating mode.
Can sunlight cause false readings?
If the sensor is in direct sun it can read high. Ensure it is in the shade of the unit casing.
