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Error code reference

LG Refrigerator Error Code fS

Freezer compartment sensor failure

LG codesLG refrigerator codes

Freezer compartment sensor failure - displayed when the freezing room sensor has a short circuit or open circuit.

First step from the service manual

Check freezer sensor resistance at POINT A voltage; 0V indicates short, 5V indicates open.

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

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What fS means on a LG refrigerator

The fS error code on an LG refrigerator indicates a failure in the freezer compartment temperature sensor. This sensor, also called the freezing room sensor, is a thermistor that continuously monitors the internal temperature of the freezer section and sends resistance-based readings to the main control board. When the control board detects that the sensor signal falls outside the expected range, it triggers the fS code to alert the user and technician that temperature monitoring has been compromised.

The fault is categorized as either a short circuit or an open circuit condition. To determine which type of failure is present, the technician checks the voltage at POINT A on the sensor circuit. A reading of 0V at that test point indicates a short circuit, meaning the sensor wiring or thermistor element has collapsed to near-zero resistance, pulling the signal line to ground. A reading of 5V at POINT A indicates an open circuit, meaning the thermistor or its wiring has broken entirely and no current is flowing through the sensor loop.

Common root causes include a failed thermistor element due to age or moisture intrusion, damaged wiring harness connections in the freezer compartment (which is subject to repeated temperature cycling and frost accumulation), or a corroded/loose connector at the control board or sensor plug. In some cases, the wiring insulation can crack in the freezer environment, creating intermittent or permanent short conditions. Diagnosing this code requires a multimeter to confirm the POINT A voltage and to measure sensor resistance directly across the thermistor terminals.

Source: manufacturer service documentation.

Common causes of fS

  1. 01

    Failed freezer thermistor

    Part replacement

    The thermistor element itself has failed due to age, moisture exposure, or physical damage, resulting in either an open or shorted resistance reading. Measuring resistance directly across the sensor terminals will confirm if it is outside the normal operating range.

  2. 02

    Damaged or broken wiring harness

    Part replacement

    The wiring between the freezer sensor and the control board can crack or break due to repeated freeze-thaw cycling in the freezer compartment. A visual inspection of the wire insulation and a continuity test along each wire will identify any breaks.

  3. 03

    Loose or corroded connector

    Wiring / connection

    The sensor plug or control board connector can loosen or corrode over time, interrupting the signal circuit. Unplugging and reseating the connector, and inspecting the terminals for corrosion or bent pins, is a quick first check.

  4. 04

    Short circuit from frost or moisture intrusion

    Wiring / connection

    Frost or condensation buildup around the sensor housing can cause a short circuit in the sensor wiring or at the connector. A 0V reading at POINT A combined with visible frost accumulation near the sensor location points to this cause.

  5. 05

    Faulty main control board

    Part replacement

    If the sensor and all wiring test within normal specifications but the fS code persists, the main control board may be misreading or failing to process the sensor signal correctly. This is the least common cause and should only be considered after all sensor and wiring checks are completed.

See the test procedure for each cause

Frequently asked questions about fS

What does fS mean on a LG refrigerator?
The fS code on an LG refrigerator indicates a freezer compartment sensor failure. Specifically, it means the freezing room thermistor has either a short circuit or an open circuit condition. The control board uses voltage readings at a specific test point to determine which type of fault is present: 0V signals a short, and 5V signals an open circuit.
Can I fix the fS error code myself?
A knowledgeable DIYer can attempt some diagnostic steps, such as inspecting the wiring harness for visible damage, reseating connectors, and testing voltage and resistance with a multimeter. If the thermistor itself has failed, replacing it is a straightforward part swap in most cases. However, if the fault traces back to the main control board, professional repair is recommended.
Is it safe to keep using my refrigerator when the fS code is displayed?
When the fS code is active, the freezer temperature sensor is not functioning reliably, which means the refrigerator cannot accurately monitor or regulate freezer temperatures. Continuing to store frozen food carries the risk of undetected temperature rises and potential spoilage. It is best to address the fault promptly and avoid relying on the freezer for critical food storage until it is resolved.
How much does it cost to repair the fS error on an LG refrigerator?
Repair costs depend on the root cause. A replacement freezer thermistor typically costs between $10 and $40 for the part alone. If professional labor is required, total repair costs including the part can range from $100 to $250 or more. A main control board replacement, if needed, will push costs higher, often into the $200 to $400 range for parts and labor combined.
Will resetting the refrigerator clear the fS error code?
A power reset, such as unplugging the refrigerator for a few minutes and plugging it back in, may temporarily clear the fS code if the fault was caused by a momentary glitch or a loose connector that reseats itself. However, if the thermistor or wiring has a genuine failure, the code will return once the control board re-evaluates the sensor signal. A persistent fS code requires physical diagnosis and likely a component repair or replacement.

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