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Error code reference

LG Refrigerator Error Code F-defrost sensor short

Freezer area defroster sensor short circuit fault

LG codesLG refrigerator codes

Freezer area defroster sensor short circuit fault - sensor reading suspected to be over +50°C.

First step from the service manual

Check F-defrost 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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  • 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 F-defrost sensor short means on a LG refrigerator

The F-defrost sensor short error on an LG refrigerator indicates a short circuit fault in the freezer compartment defrost sensor. The control board interprets a short circuit condition as a temperature reading exceeding +50°C, which is outside the normal operating range for this sensor. The defrost sensor is a negative temperature coefficient (NTC) thermistor mounted near the evaporator coil in the freezer section. Its job is to monitor evaporator temperature during the defrost cycle and signal the control board to terminate the heater once the coil has been adequately cleared of frost.

A short circuit in the sensor circuit causes resistance to drop abnormally low, which the board reads as an implausibly high temperature. Under normal operating conditions, the defrost sensor resistance changes in a predictable relationship with temperature. When the circuit shorts, this relationship breaks down entirely, and the board logs the F-defrost fault. The defrost cycle may be disrupted as a result, leading to frost accumulation on the evaporator coil over time.

The most common causes are physical damage to the sensor or its wiring harness, corrosion at connector terminals, or a failed sensor component. Ice buildup can stress wiring and cause insulation to crack, creating a short to ground or between conductors. Diagnosis should begin with a resistance check of the sensor itself, followed by a thorough inspection of the wiring harness between the sensor and the main control board.

Source: manufacturer service documentation.

Common causes of F-defrost sensor short

  1. 01

    Failed defrost sensor (thermistor)

    Part replacement

    The NTC thermistor itself has internally short-circuited, causing resistance to drop far below normal values. This is the most common root cause and is confirmed by measuring sensor resistance out of circuit and comparing it against the expected range.

  2. 02

    Damaged wiring harness

    Part replacement

    The wiring between the defrost sensor and the control board may have cracked insulation, pinched conductors, or bare wires contacting each other or the refrigerator chassis. Visually inspect the full length of the harness for any signs of wear, chafing, or ice damage.

  3. 03

    Corroded or loose connector terminals

    Wiring / connection

    Moisture in the freezer compartment can cause corrosion at the sensor connector, leading to unintended electrical contact between terminals. Inspect the connector pins for green or white oxidation and ensure the connector is fully seated.

  4. 04

    Ice accumulation forcing wiring contact

    Wiring / connection

    Excessive frost or ice buildup around the evaporator coil area can physically compress wiring and force insulated conductors together until they short. Manually defrosting the unit and then reinspecting the wiring may reveal this as the underlying issue.

  5. 05

    Faulty main control board

    Part replacement

    If the sensor and all wiring check out correctly, the control board's sensor input circuit may have failed, causing it to misread a normal signal as a short. This is the least likely cause and should only be considered after all other components are confirmed good.

See the test procedure for each cause

Frequently asked questions about F-defrost sensor short

What does F-defrost sensor short mean on a LG refrigerator?
This error means the freezer compartment defrost sensor has a short circuit fault. The control board is detecting a sensor reading that corresponds to a temperature above +50°C, which indicates the sensor or its wiring circuit is not functioning correctly. The defrost sensor is a thermistor located near the evaporator coil, and a short circuit prevents it from accurately reporting evaporator temperature during the defrost cycle.
Can I fix the F-defrost sensor short error myself?
A knowledgeable DIYer can diagnose this error by checking the defrost sensor resistance with a multimeter and visually inspecting the wiring harness for damage or corrosion. If the sensor resistance is out of specification, replacing the sensor is a straightforward repair involving the freezer back panel. However, if the fault traces back to the main control board, that repair is more complex and may warrant professional service.
Is it safe to keep using my refrigerator while this error is showing?
The refrigerator may continue cooling in the short term, but the defrost cycle could be compromised, leading to progressive frost buildup on the evaporator coil. Over time, this frost accumulation will restrict airflow and degrade cooling performance in both the freezer and fresh food compartments. It is best to address the fault promptly to prevent secondary damage.
How much does it cost to repair the F-defrost sensor short error?
If only the defrost sensor needs replacement, parts typically cost in the range of $15 to $50 depending on the specific model, making it one of the more affordable refrigerator repairs. Professional labor to diagnose and replace the sensor generally adds $80 to $150 to the total. If the main control board is at fault, parts alone can range from $100 to $300 or more.
Will resetting my LG refrigerator clear the F-defrost sensor short error?
A power reset may temporarily clear the error code from the display, but the fault will return if the underlying problem with the sensor or wiring has not been resolved. Resetting the unit does not repair a shorted sensor or damaged wiring. A proper repair requires diagnosing and replacing the faulty component before the error will stay cleared.

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