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Error code reference

Samsung Air Conditioner Error Code E312

SUMP TEMP FIXED 1 sensor error OPEN/SHORT

Samsung codesSamsung air conditioner codes

SUMP TEMP FIXED 1 sensor error OPEN/SHORT - detected when outdoor temp over -10°C.

First step from the service manual

Check if sensor connector is separated from PCB; measure resistance.

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

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What E312 means on a Samsung air conditioner

The E312 error code on a Samsung air conditioner indicates a fault with the Sump Temperature Fixed 1 sensor, specifically an open or short circuit condition detected in that sensor circuit. This fault is only triggered when the outdoor ambient temperature is above -10°C, which means the control board expects the sensor to be reading within a defined resistance range under those conditions. If the sensor signal falls outside acceptable parameters, the PCB flags the circuit as either open (broken/disconnected circuit with infinite or very high resistance) or shorted (circuit path collapsed, reading near zero ohms).

The sump temperature sensor monitors the temperature of the refrigerant sump or oil sump area in the outdoor unit. Accurate readings from this sensor are critical for compressor protection and proper system operation. When the sensor reports an implausible value, the system cannot safely regulate compressor behavior and shuts down or restricts operation to prevent damage.

The most common root causes include a disconnected sensor connector at the PCB, physical damage to the sensor wiring harness, sensor probe failure due to corrosion or heat exposure, or an actual failure of the sensor itself showing out-of-range resistance values. Diagnosis begins by visually inspecting the connector seating at the PCB and then measuring the sensor's resistance with a multimeter to confirm whether the sensor is open, shorted, or within specification for the current temperature conditions.

Source: manufacturer service documentation.

Common causes of E312

  1. 01

    Disconnected sensor connector at PCB

    Wiring / connection

    The sensor connector may have vibrated loose or was never fully seated at the outdoor unit PCB. Visually inspect the connector and firmly reseat it before any further testing.

  2. 02

    Failed sump temperature sensor (open circuit)

    Part replacement

    The sensor element itself may have broken internally, resulting in an open circuit with extremely high or infinite resistance when measured with a multimeter. A sensor reading this way must be replaced.

  3. 03

    Shorted sensor or wiring harness

    Part replacement

    Damaged insulation on the sensor wiring can cause the conductors to contact each other or a grounded surface, collapsing the resistance reading near zero ohms. Inspect the harness along its full length for chafing, pinching, or heat damage.

  4. 04

    Corrosion at sensor connector terminals

    Wiring / connection

    Moisture intrusion into the outdoor unit connector can corrode the terminal contacts, increasing resistance or breaking continuity intermittently. Clean or replace the connector if corrosion is found.

  5. 05

    Faulty outdoor unit PCB

    Part replacement

    If the sensor and all wiring check out within normal resistance specifications, the PCB sensor input circuit itself may have failed and is misreading the signal. This is the least common cause and should be confirmed only after ruling out sensor and wiring faults.

See the test procedure for each cause

Frequently asked questions about E312

What does E312 mean on a Samsung air conditioner?
E312 indicates an open or short circuit fault in the Sump Temperature Fixed 1 sensor circuit on the outdoor unit. The error is triggered when the outdoor temperature is above -10°C and the sensor is returning a signal outside the acceptable resistance range. The system uses this sensor to monitor sump temperature and protect the compressor. The fault must be resolved before normal operation can resume.
How do I fix an E312 error on my Samsung air conditioner?
Start by powering down the unit and inspecting the sensor connector at the outdoor PCB to make sure it is fully seated. Next, use a multimeter to measure the resistance of the sump temperature sensor and compare the reading to the expected value for the current ambient temperature. If the sensor reads open or shorted, replace the sensor. If the sensor reads correctly, inspect the wiring harness for damage and, as a last step, consider replacing the outdoor PCB.
Is it safe to keep running my air conditioner with an E312 error?
It is not recommended to continue running the unit with an E312 fault active. The sump temperature sensor provides critical data used to protect the compressor from overheating or operating under abnormal conditions. Running the system without a valid sensor signal risks compressor damage, which is significantly more expensive to repair than the sensor itself.
How much does it cost to repair an E312 error on a Samsung air conditioner?
If the fix is simply reseating a loose connector, there may be no parts cost, though a service call fee typically ranges from $75 to $150. Replacing the sump temperature sensor itself generally costs between $20 and $80 for the part, plus labor. If the outdoor PCB requires replacement, total repair costs can range from $250 to $600 or more depending on the model and local labor rates.
Will resetting my Samsung air conditioner clear the E312 error?
A power reset may temporarily clear the error code if the fault is intermittent, such as a connector that is partially seated. However, if the sensor or wiring has a genuine open or short circuit fault, the E312 code will return as soon as the unit restarts and the control board re-evaluates the sensor input. A reset should only be used as a diagnostic step, not as a substitute for identifying and correcting the underlying cause.

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