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Error code reference

LG Refrigerator Error Code rD

Refrigerator defrost sensor disconnection or short circuit (displays 'Lo' for disconnection, 'Hi' for short).

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Refrigerator defrost sensor disconnection or short circuit (displays 'Lo' for disconnection, 'Hi' for short).

First step from the service manual

Measure the resistance between both terminals after separating CN15 of the Main PCB. If RD-sensor is disconnected or shorted, change the RD-sensor on the evaporator.

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

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What rD means on a LG refrigerator

The rD error code on an LG refrigerator indicates a fault with the refrigerator compartment defrost sensor, also called the RD-sensor, which is mounted on the evaporator. This sensor monitors the temperature of the evaporator coil during and after defrost cycles to ensure frost is melted properly and to prevent overheating. When the main PCB detects an open circuit in the sensor loop, it displays 'Lo' alongside the rD code, indicating a disconnection. When it detects a short circuit, it displays 'Hi', indicating the sensor resistance has dropped abnormally low.

The diagnostic process centers on connector CN15 at the main PCB. With CN15 disconnected, a technician measures resistance across both terminals of the sensor circuit. A working RD-sensor will show a resistance value within its specified range at a given temperature. An open circuit reading (infinite or very high resistance) confirms a broken wire or failed sensor, while a near-zero resistance reading confirms a short. Both conditions prevent the PCB from accurately reading evaporator temperature, which can disrupt defrost cycles and lead to excessive frost buildup on the evaporator coil over time.

Common causes include physical damage to the sensor itself from ice buildup, corrosion at the sensor connector, wiring harness damage caused by repeated freeze-thaw cycles, or a failed sensor element. If the wiring and connector check out intact but resistance is still out of range, the RD-sensor mounted on the evaporator must be replaced to resolve the fault and restore normal defrost operation.

Source: manufacturer service documentation.

Common causes of rD

  1. 01

    Failed RD-sensor element

    Part replacement

    The defrost sensor on the evaporator can fail internally, causing its resistance to read as either open or shorted. This is the most common root cause when the wiring and connector are found to be intact during diagnosis.

  2. 02

    Disconnected or damaged sensor wiring harness

    Part replacement

    Repeated freeze-thaw cycles can stress and crack the wiring between the RD-sensor and connector CN15 on the main PCB, causing an open circuit. Visually inspect the harness along its full length for breaks, kinks, or corrosion.

  3. 03

    Loose or corroded CN15 connector

    Wiring / connection

    The connector at CN15 on the main PCB can become loose or corroded over time, causing an intermittent or permanent open circuit reading. Disconnecting and reseating the connector while inspecting the terminals for oxidation can identify this issue.

  4. 04

    Ice damage to the sensor

    Part replacement

    Excessive frost buildup on the evaporator can physically damage or dislodge the RD-sensor from its mounting position, breaking the sensor body or its leads. This is more likely in units that have experienced prolonged defrost cycle failures.

  5. 05

    Main PCB fault

    Part replacement

    In rare cases, the main PCB itself may be misreading the CN15 circuit even when the sensor and wiring are good. This is only considered after the sensor and full wiring harness have been confirmed functional through resistance testing.

See the test procedure for each cause

Frequently asked questions about rD

What does rD mean on a LG refrigerator?
The rD code indicates a problem with the refrigerator compartment defrost sensor located on the evaporator. When the display also shows 'Lo', the sensor circuit is open, meaning the sensor or its wiring is disconnected. When it shows 'Hi', the circuit is shorted. Both conditions prevent the control board from monitoring the evaporator temperature correctly during defrost cycles.
Can I fix the rD error myself?
A knowledgeable DIYer can start by checking the wiring harness running from the evaporator sensor to connector CN15 on the main PCB, looking for visible damage or a loose connection. However, properly diagnosing this code requires a multimeter to measure sensor resistance after disconnecting CN15. If the sensor itself has failed, replacing it on the evaporator requires disassembly of the refrigerator compartment interior panels, which is more involved and may be better suited to a technician.
Will resetting the refrigerator clear the rD error code?
Resetting the refrigerator by unplugging it or cycling the power may temporarily clear the display, but the rD code will return if the underlying sensor fault has not been corrected. The main PCB will re-detect the open or short circuit in the RD-sensor loop as soon as it runs its diagnostic checks. A permanent fix requires repairing or replacing the sensor or its wiring.
Is it safe to keep using my refrigerator while the rD code is active?
Operating the refrigerator with an active rD fault is not recommended for extended periods. Without a functioning defrost sensor, the control board cannot accurately manage defrost cycles, which can lead to heavy frost accumulation on the evaporator coil. Over time, this frost buildup will restrict airflow and cause the refrigerator to lose cooling efficiency, potentially leading to food spoilage.
How much does it cost to repair an rD error on an LG refrigerator?
Repair costs vary depending on whether the issue is a simple connector reseating, a wiring repair, or a full sensor replacement. A replacement RD-sensor part typically costs in the range of $20 to $60 depending on the specific model. If a technician is hired for diagnosis and replacement, total costs including labor generally fall in the range of $100 to $250. Main PCB replacement, if ever required, would be significantly more expensive.

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