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Error code reference

Samsung Air Conditioner Error Code E399

Heat sink temperature sensor error of Fan2.

Samsung codesSamsung air conditioner codes
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What the E399 error code actually means

Your Samsung air conditioner has detected a problem with the temperature sensor on the cooling fin assembly for one of its internal fans. This sensor monitors heat levels to protect the unit's electronics, and the system has stopped normal operation because the sensor is giving an unexpected reading. A technician will need to inspect the sensor, its wiring, and the surrounding components to identify the exact cause.

Diagnostic procedure

The full E399 procedure

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1
Confirm the fault
Power cycle the unit: switch off the breaker for 60 seconds, then restore power. If the code returns, the fault is persistent and the procedure below isolates the cause.
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Most common causes of E399

Ranked by how often they cause this code
  1. 1Faulty heat sink thermistor
  2. 2Damaged or corroded sensor wiring harness
  3. 3Control board input circuit failure
  4. 4Overheating due to restricted airflow
  5. 5Poor sensor mounting contact

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Questions people ask about E399

What does E399 mean on a Samsung air conditioner?
E399 indicates a heat sink temperature sensor error for the Fan2 module on your Samsung air conditioner. The sensor monitors the temperature of the power electronics associated with the second fan circuit, and the control system has detected a reading outside the acceptable range. This can result from a failed sensor, wiring issues, or an actual overheating condition at the heat sink.
Is it safe to run my air conditioner with the E399 error active?
It is not recommended to continue running the unit while E399 is active. The error indicates a fault in the thermal protection circuit for the Fan2 module, which means the system may not be able to detect or respond to overheating conditions in the power electronics. Continued operation without resolving the fault could result in damage to the inverter board or related components.
How much does it cost to repair an E399 error on a Samsung air conditioner?
Repair costs depend on the root cause. Replacing a thermistor sensor is generally on the lower end of the cost spectrum, typically in the range of $75 to $200 including labor. If the control board or inverter module requires replacement, costs can range from $300 to $700 or more depending on the model and local labor rates. A diagnostic service call is usually required first to confirm the faulty component.
Can I fix E399 myself, or do I need a technician?
Some basic checks, such as inspecting for blocked airflow and cleaning filters, can be done without professional help. However, diagnosing the thermistor, testing the wiring harness for continuity, and evaluating the control board requires electrical testing tools and knowledge of inverter drive circuits. Most homeowners will need a qualified HVAC technician to resolve this error safely and correctly.
Will resetting my Samsung air conditioner clear the E399 error?
A power reset may temporarily clear the error code, but if the underlying fault persists, the code will return once the unit resumes operation and the control system re-evaluates the sensor signal. Resetting is useful for ruling out a transient fault, but a recurring E399 requires proper diagnosis of the sensor, wiring, and control board.

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