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Error code reference

LG Refrigerator Error Code R-defrost sensor open

Refrigerator area defroster sensor open circuit fault

LG codesLG refrigerator codes

Refrigerator area defroster sensor open circuit fault - sensor reading suspected to be below -50°C.

First step from the service manual

Check R-defrost sensor resistance and wiring; replace sensor if faulty.

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

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
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What R-defrost sensor open means on a LG refrigerator

The R-defrost sensor open fault indicates that the refrigerator compartment defrost sensor has developed an open circuit condition. The refrigerator's control board monitors this sensor continuously, and when the resistance reading falls outside the expected range, corresponding to a temperature below -50°C, the board logs this fault. The defrost sensor is a negative temperature coefficient (NTC) thermistor positioned near the evaporator coil in the refrigerator section, responsible for signaling the control board when to terminate a defrost cycle once the coil has cleared ice buildup.

An open circuit in this sensor means the control board is receiving either no signal or a signal so far out of range that it interprets the temperature as impossibly low. This prevents the defrost system from operating correctly. Without accurate sensor input, the refrigerator may fail to defrost the evaporator coil on schedule, which can eventually lead to ice accumulation, reduced airflow, and declining cooling performance throughout the refrigerator compartment.

The most common causes of this fault are a physically broken or disconnected sensor, damaged wiring in the sensor harness, or a corroded connector. Cold temperatures and moisture near the evaporator coil can degrade connectors over time. Diagnosis involves measuring the sensor's resistance with a multimeter and inspecting the wiring harness from the sensor back to the main control board. A faulty sensor must be replaced to restore proper defrost cycle operation.

Source: manufacturer service documentation.

Common causes of R-defrost sensor open

  1. 01

    Failed defrost sensor (open thermistor)

    Part replacement

    The NTC thermistor inside the sensor has internally broken, creating an open circuit. This is the most common cause and is confirmed by measuring infinite or out-of-range resistance across the sensor terminals with a multimeter.

  2. 02

    Broken or damaged sensor wiring

    Part replacement

    The wire leads running from the defrost sensor to the wiring harness can crack or break due to repeated freeze-thaw cycling and physical stress. Inspect the full length of the sensor wires for visible breaks, kinks, or fraying.

  3. 03

    Corroded or disconnected wiring connector

    Wiring / connection

    Moisture near the evaporator coil can corrode the connector pins where the sensor plugs into the harness, increasing resistance to the point of an open circuit. Check the connector for oxidation, bent pins, or a loose fit.

  4. 04

    Damaged wiring harness between sensor and control board

    Part replacement

    Chafing or pinching of the harness further along its route to the main control board can interrupt the circuit. A continuity test along the harness will identify any break in the circuit.

  5. 05

    Faulty main control board

    Part replacement

    If the sensor and all wiring test within spec, the control board's sensor input circuit may have failed. This is the least likely cause and should only be considered after the sensor and harness are confirmed to be in good condition.

See the test procedure for each cause

Frequently asked questions about R-defrost sensor open

What does R-defrost sensor open mean on a LG refrigerator?
This error means the defrost sensor located in the refrigerator compartment, near the evaporator coil, has an open circuit. The control board interprets the sensor reading as below -50°C, which indicates the sensor is not sending a valid signal. The fault affects the automatic defrost cycle, which relies on this sensor to know when the evaporator coil has been fully defrosted. Diagnosis involves checking the sensor's resistance and inspecting its wiring.
Can I fix the R-defrost sensor open error myself?
A knowledgeable DIYer can diagnose this fault by unplugging the refrigerator, locating the defrost sensor near the evaporator coil, and measuring its resistance with a multimeter. If the sensor reads open or infinite resistance, it needs to be replaced. Wiring connectors should also be inspected and cleaned if corrosion is present. If the sensor and wiring appear fine, further diagnosis of the control board is best left to a technician.
Is it safe to keep using my LG refrigerator while this error is active?
Short-term use may be possible, but operating the refrigerator with a non-functional defrost sensor is not recommended for extended periods. Without a working sensor, the defrost cycle cannot terminate properly, which can allow ice to accumulate on the evaporator coil. This ice buildup will eventually restrict airflow, reduce cooling performance, and could lead to food spoilage or additional component damage.
Will resetting my LG refrigerator clear the R-defrost sensor open error?
A reset may temporarily clear the fault code from the display, but the error will return if the underlying problem with the sensor or its wiring has not been resolved. The control board will continue to detect the open circuit condition every time it checks the sensor input. A permanent fix requires repairing or replacing the faulty sensor or wiring.
How much does it cost to fix the R-defrost sensor open error on an LG refrigerator?
Repair costs vary depending on whether it is a DIY repair or a professional service call. A replacement defrost sensor part typically falls in the range of $15 to $50. If a technician is hired, total costs including labor can range from $100 to $250 depending on your location and the extent of any wiring repairs needed. If the main control board is ultimately found to be at fault, parts and labor costs will be higher.

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