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Error code reference

LG Refrigerator Error Code R-DEFROST SENSOR ERROR

Refrigerator defrost sensor fault

LG codesLG refrigerator codes

Refrigerator defrost sensor fault — sensor housing slip-out, contact defect, wire cut, wire short, or sensor temperature out of range.

First step from the service manual

Check voltage between Main PCB CN30 pins 6↔8; it shall be within 4.5V~1.0V.

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 ERROR means on a LG refrigerator

The R-DEFROST SENSOR ERROR on an LG refrigerator indicates a fault within the refrigerator compartment defrost sensor circuit. This sensor monitors temperature during the defrost cycle to prevent the evaporator from overheating and to signal the control board when defrost is complete. The Main PCB reads the sensor's resistance through connector CN30, specifically between pins 6 and 8, and converts that resistance into a voltage signal. Under normal operating conditions, the voltage at those pins should fall between 1.0V and 4.5V, corresponding to the expected temperature range the sensor encounters during normal and defrost operation.

When the control board detects a voltage outside this 1.0V to 4.5V window, or detects an open or shorted circuit, it logs the R-DEFROST SENSOR ERROR and may suspend defrost operation. The five root causes recognized for this fault are: the sensor housing slipping out of its mounting clip on the evaporator, a contact defect at the sensor connector, a cut or broken wire in the sensor harness, a short circuit within the wiring, or the sensor itself reading a temperature outside its calibrated range due to component failure.

Diagnosis begins at CN30 on the Main PCB. Measuring voltage between pins 6 and 8 immediately reveals whether the problem is in the sensor, the wiring, or the board itself. A reading of 0V or above 4.5V points to an open wire or a disconnected sensor. A reading pinned low can indicate a short to ground in the harness. If wiring continuity checks out, the sensor's resistance should be measured directly and compared against the expected temperature-resistance curve to confirm whether the sensor element itself has drifted or failed.

Source: manufacturer service documentation.

Common causes of R-DEFROST SENSOR ERROR

  1. 01

    Sensor connector contact defect

    Wiring / connection

    Corrosion, bent pins, or a loose connection at the CN30 harness connector on the Main PCB or at the sensor plug can interrupt the signal. Inspect both ends of the connector for oxidation or physical damage and reseat firmly.

  2. 02

    Sensor housing slip-out from evaporator mount

    Wiring / connection

    The defrost sensor clips onto the evaporator coil, and vibration or ice buildup can cause it to dislodge. A displaced sensor will read inaccurate temperatures, pushing the voltage outside the 1.0V to 4.5V range.

  3. 03

    Failed defrost sensor element

    Part replacement

    The thermistor inside the sensor can drift or fail outright, producing resistance values that fall outside the expected temperature-resistance curve. This results in a voltage at CN30 pins 6 to 8 that is too high, too low, or erratic.

  4. 04

    Cut or broken sensor wire

    Part replacement

    Physical damage to the wiring harness between the sensor and the Main PCB, often caused by ice buildup, sharp cabinet edges, or prior service work, will produce an open circuit and a voltage reading outside the valid range.

  5. 05

    Short circuit in sensor wiring

    Part replacement

    A pinched or chafed wire can short to ground or to another conductor in the harness, pulling the signal voltage down and triggering the error. Inspect the full length of the harness for damage, especially near routing clips and panel edges.

See the test procedure for each cause

Frequently asked questions about R-DEFROST SENSOR ERROR

What does R-DEFROST SENSOR ERROR mean on a LG refrigerator?
The R-DEFROST SENSOR ERROR means the Main PCB has detected a problem with the refrigerator compartment defrost sensor circuit. The board monitors voltage between pins 6 and 8 of connector CN30, and a reading outside the 1.0V to 4.5V range triggers this fault. The cause can be a loose or corroded connector, a dislodged sensor, a broken wire, a wiring short, or a sensor that has failed internally.
Can I fix the R-DEFROST SENSOR ERROR myself?
Some causes are DIY-friendly. Reseating the sensor into its evaporator mounting clip or reconnecting a loose harness plug requires no special tools. Checking the voltage at CN30 pins 6 and 8 with a multimeter is also straightforward. Replacing the defrost sensor or repairing a damaged wiring harness is within reach for someone comfortable working with basic appliance wiring, but if the Main PCB itself is faulty, professional service is recommended.
Is it safe to keep using my refrigerator while this error is active?
Short-term use is generally possible, but the defrost cycle may be suspended while the error is active, which means frost can accumulate on the evaporator coil over time. Heavy frost buildup will eventually block airflow and cause the refrigerator to lose cooling capacity. It is best to diagnose and address the fault promptly to prevent food spoilage or damage to other components.
How much does it cost to repair an R-DEFROST SENSOR ERROR on an LG refrigerator?
If the fix is simply reseating the sensor or reconnecting a loose plug, there is no parts cost. A replacement defrost sensor typically costs in the range of $15 to $60 for the part alone. If a technician is needed, total repair costs including labor generally range from $100 to $250, depending on local rates and whether additional components such as the wiring harness or Main PCB need to be replaced.
Will resetting the refrigerator clear the R-DEFROST SENSOR ERROR?
A power reset may temporarily clear the error code from the display, but the fault will return if the underlying problem has not been fixed. The Main PCB continuously monitors the voltage at CN30 pins 6 and 8, so any sensor, wiring, or connector issue will cause the error to reappear. A reset is useful for confirming whether the fault is intermittent, but it is not a substitute for proper diagnosis and repair.

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