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Error code reference

Samsung Air Conditioner Error Code E408

Fixed capacity compressor 1 discharge sensor OPEN/SHORT error

Samsung codesSamsung air conditioner codes

Fixed capacity compressor 1 discharge sensor OPEN/SHORT error. Detected when outdoor temp over -10°C.

First step from the service manual

Check sensor connector; measure resistance across both terminals.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What E408 means on a Samsung air conditioner

Error code E408 on a Samsung air conditioner indicates a fault with the discharge temperature sensor on fixed capacity compressor 1 in the outdoor unit. This sensor monitors the temperature of refrigerant as it exits the compressor, which is a critical measurement for protecting the compressor from overheating and for regulating system operation. The error is triggered when the control board detects either an open circuit or a short circuit condition at this sensor, and it is only flagged when the outdoor ambient temperature is above -10°C, which eliminates false triggers caused by extreme cold affecting sensor resistance values.

The discharge sensor is a negative temperature coefficient (NTC) thermistor. In a normal operating range, the resistance across its terminals falls within a predictable curve relative to temperature. An open circuit condition means the resistance reads extremely high or infinite, indicating a broken wire, corroded connector pin, or failed sensor element. A short circuit condition means resistance reads near zero, typically caused by damaged insulation allowing the two wires to contact each other or a failed thermistor with internal short.

Diagnosis begins at the sensor connector on the outdoor unit control board. Disconnect the connector and measure resistance across the two sensor terminals using a multimeter. If the reading is infinite or near zero ohms and does not shift with temperature changes, the sensor itself has failed. If the connector shows corrosion, moisture intrusion, or backed-out pins, the wiring harness may be at fault rather than the sensor. Refrigerant leaks in the vicinity of the discharge line can also accelerate sensor degradation over time.

Source: manufacturer service documentation.

Common causes of E408

  1. 01

    Failed discharge temperature sensor

    Part replacement

    The NTC thermistor sensor element itself has failed, producing either an open or short circuit reading. This is the most common cause and is confirmed by measuring resistance across the sensor terminals and finding a reading of near-zero or infinite ohms.

  2. 02

    Damaged or corroded sensor connector

    Wiring / connection

    Moisture, vibration, or corrosion at the connector between the sensor and the outdoor unit control board can cause intermittent or complete loss of signal. Inspect the connector for green corrosion, bent pins, or signs of water intrusion.

  3. 03

    Broken or shorted sensor wiring

    Part replacement

    The wiring harness running from the discharge sensor to the control board can be pinched, chafed, or cut, resulting in an open or short condition. Trace the harness from the sensor to the board and look for visible damage or contact with sharp metal edges.

  4. 04

    Faulty outdoor unit control board

    Part replacement

    If the sensor and wiring both test within normal resistance values, the input circuit on the control board may have failed, causing it to misread the sensor signal. This is the least common cause and is only confirmed after ruling out all wiring and sensor faults.

See the test procedure for each cause

Frequently asked questions about E408

What does E408 mean on a Samsung air conditioner?
E408 indicates an open or short circuit fault on the fixed capacity compressor 1 discharge temperature sensor in the outdoor unit. The control board cannot obtain a valid temperature reading from this sensor. The error is only triggered when outdoor temperatures are above -10°C. The system will shut down or restrict operation to protect the compressor until the fault is resolved.
Can I fix E408 myself, or do I need a technician?
A knowledgeable DIYer can check the sensor connector for corrosion and measure resistance across the sensor terminals with a multimeter to determine if the sensor has failed. However, accessing the outdoor unit control board and replacing components in a refrigerant-containing system often requires professional experience. If the sensor wiring or the board itself needs replacement, a certified HVAC technician is the safer choice.
Is it safe to run my air conditioner with an E408 error?
You should not continue operating the unit with E408 active. The discharge temperature sensor is a primary protection component for the compressor. Without accurate discharge temperature data, the system cannot detect overheating conditions, which can lead to compressor failure. Running the system in a faulted state risks expensive secondary damage.
Will resetting the air conditioner clear the E408 error?
A power reset may temporarily clear the error code, but it will return as soon as the system attempts to operate and the control board re-detects the open or short condition at the sensor. The underlying wiring or sensor fault must be physically repaired before the code will stay cleared.
How much does it cost to repair an E408 error on a Samsung air conditioner?
If only the discharge temperature sensor needs replacement, parts and labor typically range from $75 to $200 depending on the unit model and local service rates. If the issue is a wiring harness, costs are similar. Replacement of the outdoor control board is more expensive and can range from $200 to $600 or more including labor. Getting a diagnostic inspection first helps narrow down the actual failed component before committing to parts costs.

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