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Error code reference

LG Refrigerator Error Code F-sensor open

Freezer room temperature sensor open circuit fault

LG codesLG refrigerator codes

Freezer room temperature sensor open circuit fault - sensor reading suspected to be below -50°C.

First step from the service manual

Check F-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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What F-sensor open means on a LG refrigerator

The F-sensor open error on an LG refrigerator indicates an open circuit fault in the freezer compartment temperature sensor (thermistor). The control board interprets an open circuit as a sensor reading below -50°C, which falls outside the valid operating range for the sensor. This triggers the fault code because the board can no longer receive a reliable temperature signal from the freezer and cannot regulate the compressor or evaporator fan cycles accurately.

The freezer temperature sensor is a negative temperature coefficient (NTC) thermistor, meaning its electrical resistance decreases as temperature rises. Under normal freezer operating conditions, the sensor produces a measurable resistance value that the control board reads as a specific temperature. When the circuit is open, resistance becomes effectively infinite, and the board logs the F-sensor open fault. Common causes include a broken sensor wire, a damaged connector, or internal failure of the thermistor itself.

Diagnosing this fault begins with a visual inspection of the sensor wiring harness and connector for corrosion, pinching, or breaks. Following that, the technician should measure the sensor resistance directly at the thermistor terminals using a multimeter. A sensor in good condition will show a finite resistance value consistent with the ambient freezer temperature. An open circuit reading (OL or infinite resistance) confirms sensor failure. If wiring and connectors check out, the sensor itself should be replaced.

Source: manufacturer service documentation.

Common causes of F-sensor open

  1. 01

    Failed freezer temperature sensor (thermistor)

    Part replacement

    The thermistor itself has developed an internal open circuit and is no longer conducting. Measuring resistance directly at the sensor terminals will return an infinite or OL reading, confirming the component has failed.

  2. 02

    Broken or damaged sensor wiring

    Wiring / connection

    The wire harness running from the freezer sensor to the control board can become pinched, cracked, or broken, interrupting the circuit. A visual inspection along the full length of the harness and a continuity test will identify any breaks.

  3. 03

    Corroded or loose sensor connector

    Wiring / connection

    The connector joining the sensor to the wiring harness can loosen over time or accumulate corrosion, creating an intermittent or permanent open circuit. Inspect the connector pins for oxidation, moisture damage, or poor seating.

  4. 04

    Control board failure

    Part replacement

    In less common cases, the control board input circuit for the F-sensor may be faulty, causing it to misread a functioning sensor as open. This should only be suspected after the sensor and wiring have been confirmed good.

See the test procedure for each cause

Frequently asked questions about F-sensor open

What does F-sensor open mean on a LG refrigerator?
The F-sensor open code means the freezer compartment temperature sensor has an open circuit fault, and the control board is receiving no valid resistance signal from it. The board interprets this condition as a temperature reading below -50°C, which is outside the normal operating range. This prevents the refrigerator from accurately monitoring freezer temperatures. The cause is typically a failed thermistor, broken wiring, or a faulty connector.
How do I fix the F-sensor open error on my LG refrigerator?
Start by unplugging the refrigerator and inspecting the freezer temperature sensor wiring harness and connector for visible damage, corrosion, or loose connections. Use a multimeter to check continuity in the wiring and measure resistance at the sensor terminals. If the sensor reads open circuit (infinite resistance), the thermistor needs to be replaced. If wiring and sensor test normal, the control board may need further evaluation.
Is my food safe when the F-sensor open error is showing?
Food safety depends on how long the error has been active and whether the freezer is still maintaining adequate cold temperatures. Without a functioning sensor, the refrigerator cannot properly regulate the freezer, so temperatures may rise over time. Check the actual freezer temperature with a thermometer and transfer perishables if the temperature has climbed above 0°F (-18°C). Address the fault as soon as possible to avoid further food spoilage risk.
Will resetting my LG refrigerator clear the F-sensor open error?
A power reset may temporarily clear the error code from the display, but if the underlying fault in the sensor or wiring has not been repaired, the code will return once the control board performs its diagnostic checks again. A reset is useful for confirming whether the fault is intermittent, but it is not a substitute for diagnosing and repairing the open circuit condition.
How much does it cost to fix the F-sensor open error on an LG refrigerator?
If only the freezer temperature sensor needs replacement, parts typically cost in the range of $15 to $50 depending on the specific model. If a service technician is needed for diagnosis and installation, total repair costs including labor generally range from $100 to $250. Control board replacement, if required, would increase costs significantly above that range. Getting a diagnosis first helps avoid unnecessary parts replacement.

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