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Error code reference

LG Refrigerator Error Code R1 R3 ON

Refrigerator sensor open or short circuit.

LG codesLG refrigerator codes

Refrigerator sensor open or short circuit.

First step from the service manual

Check each sensor.

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

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What R1 R3 ON means on a LG refrigerator

The R1 R3 ON error code on an LG refrigerator indicates that one or more of the refrigerator compartment temperature sensors has developed an open circuit or short circuit condition. These sensors, typically negative temperature coefficient (NTC) thermistors, are responsible for monitoring the internal temperature of the refrigerator section and relaying that data to the main control board. When a sensor reads outside its expected resistance range, the control board flags the fault and displays this error to alert the technician that the temperature monitoring system is compromised.

An open circuit in a thermistor means the sensor's electrical path has been broken, resulting in an infinitely high resistance reading that the control board cannot interpret. A short circuit, by contrast, means resistance has dropped to near zero, causing the board to read an implausibly low temperature. Both conditions prevent accurate temperature regulation, which can result in the refrigerator running continuously, failing to cool properly, or cycling erratically. The R1 and R3 designations refer to specific sensor positions within the refrigerator compartment, and both being flagged simultaneously can indicate a wiring harness issue shared between the two sensor circuits.

Diagnosis should begin by physically inspecting each sensor and its associated wiring for visible damage, corrosion, or loose connectors. Resistance testing across each thermistor with a multimeter at a known temperature will confirm whether the sensor itself has failed or whether the fault lies in the wiring between the sensor and the control board.

Source: manufacturer service documentation.

Common causes of R1 R3 ON

  1. 01

    Failed refrigerator thermistor (sensor)

    Part replacement

    The NTC thermistor itself has developed an internal open or short circuit, causing it to read outside the acceptable resistance range. This is the most common cause and is confirmed by measuring the sensor's resistance with a multimeter and comparing it to the expected value at a known temperature.

  2. 02

    Damaged or corroded wiring harness

    Wiring / connection

    The wiring connecting the R1 or R3 sensor to the main control board may have a break, pinch, or corroded connector, creating an open or short in the circuit. Inspect the full wire run from each sensor to the control board for visible damage or moisture intrusion.

  3. 03

    Loose or disconnected sensor connector

    Wiring / connection

    The sensor connector may have worked loose from the control board or from the sensor itself, interrupting the circuit and triggering the error. Check all connector seating points and re-seat any that feel loose or show signs of intermittent contact.

  4. 04

    Moisture or ice buildup at the sensor

    Wiring / connection

    Excessive ice accumulation in the refrigerator compartment can encase a sensor or its connector, causing a circuit fault. A full manual defrost of the compartment and then retesting the sensor resistance can help determine if moisture was the root cause.

  5. 05

    Faulty main control board

    Part replacement

    If both sensors and all associated wiring test within normal parameters, the main control board itself may have failed and may be misreading or not properly communicating with the sensor inputs. This is the least common cause and should be diagnosed only after ruling out the sensors and wiring.

See the test procedure for each cause

Frequently asked questions about R1 R3 ON

What does R1 R3 ON mean on a LG refrigerator?
The R1 R3 ON error code means the refrigerator has detected an open circuit or short circuit in one or more of the refrigerator compartment temperature sensors. These sensors are thermistors that monitor internal temperature and send readings to the main control board. When a sensor's resistance reading falls outside the expected range, the board flags this error. The refrigerator may not cool properly while this fault is active.
How do I fix the R1 R3 ON error on my LG refrigerator?
Start by inspecting the wiring and connectors for the R1 and R3 sensors, looking for breaks, corrosion, or loose connections and re-seating any connectors that appear loose. Use a multimeter to test the resistance of each thermistor to determine if a sensor has failed internally. If a sensor tests as open or shorted, replace it. If the sensors and wiring both check out, the main control board may need to be evaluated.
Is it safe to use my LG refrigerator while the R1 R3 ON error is displayed?
Operating the refrigerator with this error is not recommended for extended periods because the control board cannot accurately regulate compartment temperature without functioning sensors. Food safety may be at risk if the refrigerator is not maintaining proper temperatures. It is best to check internal temperatures with a standalone thermometer and address the fault promptly.
Will resetting my LG refrigerator clear the R1 R3 ON error?
A reset may temporarily clear the error code from the display, but it will return if the underlying sensor or wiring fault has not been corrected. Resetting is useful for confirming whether the fault is intermittent, but it is not a fix. The root cause, whether a failed thermistor, damaged wiring, or a bad connection, must be identified and repaired to permanently resolve the code.
How much does it cost to repair the R1 R3 ON error on an LG refrigerator?
Repair costs vary depending on what component has failed. Replacement thermistor sensors are relatively inexpensive, typically in the range of $10 to $40 per sensor for parts. If the main control board is at fault, parts costs can range from $100 to $300 or more. Adding a technician's labor charge will increase the total, generally bringing a professional repair to somewhere between $100 and $400 depending on the specific failure and local labor rates.

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