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Error code reference

Samsung Air Conditioner Error Code E256

Compressor OLP sensor error (Short/Open)

Samsung codesSamsung air conditioner codes

Compressor OLP sensor error (Short/Open) - error check condition: outdoor temp over -20°C, error level over 4.95V (-30°C) or under 0.5V (151°C).

First step from the service manual

Check OLP temperature sensor.

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

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What E256 means on a Samsung air conditioner

The E256 error code on a Samsung air conditioner indicates a fault with the compressor OLP (Over-Load Protector) temperature sensor. This sensor monitors the thermal condition of the compressor to prevent damage from excessive heat or abnormal operating conditions. The error is triggered when the outdoor ambient temperature is above -20°C and the sensor signal voltage falls outside the acceptable operating window, specifically above 4.95V or below 0.5V. These voltage thresholds correspond to temperature readings that are physically implausible for the sensor circuit: a voltage above 4.95V correlates to a temperature reading below -30°C, while a voltage below 0.5V corresponds to a reading above 151°C.

The OLP sensor is a thermistor-based device positioned on or near the compressor body in the outdoor unit. It feeds a voltage signal to the outdoor control board, which the board interprets as a real-time temperature value. When the signal voltage reaches either extreme boundary, the system interprets the condition as a short circuit (very low resistance driving voltage low) or an open circuit (very high resistance driving voltage high). Both conditions render the sensor reading unreliable, so the system faults out to protect the compressor from operating without valid thermal feedback.

Common causes include a failed OLP sensor with a degraded thermistor element, damaged wiring between the sensor and the control board such as cuts, corrosion, or connector pin damage, and in some cases a faulty outdoor control board that misreads the sensor signal. Diagnosis should begin at the sensor itself, checking resistance values and connector integrity before proceeding to wiring harness continuity and board-level evaluation.

Source: manufacturer service documentation.

Common causes of E256

  1. 01

    Failed OLP temperature sensor

    Part replacement

    The thermistor element inside the OLP sensor can degrade or fail completely, resulting in a resistance value that drives the signal voltage outside the 0.5V to 4.95V operating range. Disconnect the sensor and measure its resistance to check whether it falls within the expected range for the ambient temperature.

  2. 02

    Damaged or corroded sensor wiring

    Wiring / connection

    Wiring between the OLP sensor and the outdoor control board can develop cuts, pinch points, or corrosion at connectors, causing an open or near-short condition that mimics a sensor failure. Visually inspect the entire wire run and check connector pins for oxidation or looseness.

  3. 03

    Loose or disconnected sensor connector

    Wiring / connection

    A partially seated or fully disconnected connector at the sensor or the control board will produce an open-circuit voltage reading above 4.95V. Check both ends of the sensor harness to confirm the connectors are fully seated and locked.

  4. 04

    Moisture ingress into sensor or connector

    Part replacement

    Water intrusion into the outdoor unit can cause leakage current between connector pins or inside the sensor body itself, pulling the signal voltage to an abnormal level. Inspect for signs of water damage, corrosion, or tracking marks on the connector housing.

  5. 05

    Faulty outdoor control board

    Part replacement

    If the sensor resistance and all wiring check out correctly, the outdoor control board's sensor input circuit may be damaged, causing it to misinterpret or not read the sensor voltage accurately. Board-level faults are the least common cause and should be diagnosed only after the sensor and harness are confirmed good.

See the test procedure for each cause

Frequently asked questions about E256

What does E256 mean on a Samsung air conditioner?
E256 indicates a compressor OLP (Over-Load Protector) sensor error caused by a signal voltage that is either above 4.95V or below 0.5V when the outdoor temperature is above -20°C. These voltage extremes indicate an open circuit or short circuit condition in the sensor or its wiring. The system disables operation to protect the compressor from running without valid thermal monitoring.
Can I fix the E256 error myself?
A knowledgeable DIYer can inspect and reseat the OLP sensor connector and check the wiring harness for visible damage without special tools. Measuring sensor resistance to confirm whether the thermistor has failed does require a multimeter but is straightforward. Replacing the sensor or outdoor control board involves working inside the outdoor unit, and refrigerant-side work must be handled by a certified technician.
Is it safe to keep running the air conditioner with an E256 error?
No. The E256 error means the system cannot reliably monitor the compressor's thermal condition, so the unit will typically lock out operation automatically. Attempting to bypass or repeatedly reset the system without fixing the underlying fault risks running the compressor without proper over-temperature protection, which can lead to compressor failure.
Will resetting the air conditioner clear the E256 error?
A power reset may temporarily clear the error code, but E256 will return if the root cause has not been repaired. The fault condition is checked continuously when the outdoor temperature is above -20°C, so the code will reappear as soon as the system re-evaluates the sensor signal and finds it out of range. A permanent fix requires repairing or replacing the faulty sensor or wiring.
How much does it cost to repair an E256 error on a Samsung air conditioner?
Repair costs depend on what component has failed. Replacing the OLP temperature sensor typically ranges from around $50 to $150 for parts and labor. If the outdoor control board is the cause, parts and labor can range from $200 to $500 or more depending on the model and service rates in your area. A diagnostic visit from a technician is usually required to confirm the exact fault before parts are ordered.

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