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Error code reference

Samsung Air Conditioner Error Code E304

COND-OUT SUB 1 temperature sensor error OPEN/SHORT.

Samsung codesSamsung air conditioner codes

COND-OUT SUB 1 temperature sensor error OPEN/SHORT.

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What E304 means on a Samsung air conditioner

The E304 error code on a Samsung air conditioner indicates a fault with the COND-OUT SUB 1 temperature sensor, which monitors the temperature of the refrigerant or surrounding area at the condenser outlet. This sensor is a thermistor, meaning its electrical resistance changes predictably with temperature. The designations OPEN and SHORT refer to the two failure modes the control board detects: an open circuit means the sensor circuit has broken continuity and is reading infinite or out-of-range high resistance, while a short circuit means the resistance has dropped abnormally low, essentially to near zero. Both conditions produce temperature readings that fall outside the acceptable operating range, causing the system to fault and halt operation to prevent equipment damage.

The condenser outlet sub-sensor (labeled SUB 1) is typically positioned to monitor refrigerant temperature as it exits the condenser coil, providing data the control board uses to manage system efficiency, compressor protection, and refrigerant charge diagnostics. When this sensor fails or its wiring is compromised, the board can no longer trust the thermal data from that circuit and triggers E304 as a protective measure.

Common causes include physical damage to the sensor probe itself from corrosion, vibration, or moisture intrusion, as well as wiring harness faults such as pinched wires, corroded connectors, or broken terminals between the sensor and the main control board. In some cases, the sensor has simply reached end of life and its thermistor element has drifted out of specification.

Source: manufacturer service documentation.

Common causes of E304

  1. 01

    Failed COND-OUT SUB 1 thermistor

    Part replacement

    The thermistor element inside the sensor probe has failed, causing its resistance to read either open (infinite) or shorted (near zero). This can be confirmed by disconnecting the sensor and measuring its resistance with a multimeter to see if the reading falls completely out of the expected range for the ambient temperature.

  2. 02

    Corroded or damaged sensor connector

    Wiring / connection

    Moisture and outdoor exposure can corrode the connector pins where the sensor plugs into the wiring harness, creating high resistance or an intermittent open circuit. Inspect the connector for green or white corrosion, bent pins, or loose terminal seats.

  3. 03

    Damaged wiring harness

    Wiring / connection

    The wire run from the sensor to the control board can be pinched, cut, or abraded by vibration or sharp cabinet edges, resulting in an open or short condition. Carefully trace the wiring from the sensor through the harness, checking for visible damage or areas where insulation has worn through.

  4. 04

    Faulty main control board

    Part replacement

    If the sensor and all wiring test within normal resistance specifications, the control board input circuit for this sensor channel may have failed. This is a less common cause and should only be considered after the sensor and wiring have been ruled out.

See the test procedure for each cause

Frequently asked questions about E304

What does E304 mean on a Samsung air conditioner?
E304 indicates that the COND-OUT SUB 1 temperature sensor at the condenser outlet has triggered an OPEN or SHORT fault. This means the control board is detecting that the sensor circuit has either lost continuity or has shorted out, producing an invalid temperature reading. The system shuts down to prevent potential damage to the compressor or refrigerant circuit.
Can I fix the E304 error myself?
A knowledgeable DIYer can inspect the sensor connector and wiring harness for visible corrosion or damage, and can test the thermistor resistance with a multimeter. However, if the sensor itself needs replacement or the fault is traced to the control board, working on the outdoor condenser unit involves handling electrical components that may carry line voltage, so hiring a certified technician is strongly recommended for those repairs.
Is it safe to run my air conditioner with an E304 error?
No. When E304 is active, the system has typically shut itself down as a protective measure because it cannot monitor condenser outlet temperature accurately. Attempting to bypass or ignore this fault and force the unit to run risks compressor damage or refrigerant system issues. The fault should be diagnosed and repaired before resuming normal operation.
Will resetting the unit clear the E304 error?
A power reset may temporarily clear the error code, but if the underlying sensor or wiring fault is still present, the E304 code will return once the system restarts and begins reading from the sensor again. A reset is only a valid fix if the fault was caused by a one-time transient condition, which is rare for this error type.
How much does it cost to repair an E304 error on a Samsung air conditioner?
Repair costs depend on what component has failed. A replacement thermistor sensor typically costs in the range of $20 to $80 for the part, while a control board can range from $100 to $300 or more. Adding labor charges for a qualified HVAC technician, total repair costs commonly fall between $100 and $500 depending on the diagnosis, the specific model, and local labor rates.

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