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Error code reference

LG Refrigerator Error Code F-DEFROSTING ERROR

F compartment defrosting heater error

LG codesLG refrigerator codes

F compartment defrosting heater error: electric wire cut, short-circuit, contact failure, sensor housing missing, or defective temperature fuse; defrost not finished after continuous heating for more than 80 min.

First step from the service manual

After separating Main PCB CN70 wire from the PCB, check resistance between brown ↔ orange color to see if it is between 150 and 200Ω.

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

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What F-DEFROSTING ERROR means on a LG refrigerator

The F-DEFROSTING ERROR on an LG refrigerator indicates a fault in the F compartment defrost heater circuit. This error triggers when the control system detects that defrost has not completed after the heater has been running continuously for more than 80 minutes. The F compartment defrost system relies on a heater element, a defrost temperature sensor, and a thermal fuse working together. If any of these components fail, or if wiring connections are broken or shorted, the heater cannot properly melt frost accumulation and the system flags this error.

The primary diagnostic entry point involves the Main PCB connector CN70. After disconnecting the CN70 wire harness from the PCB, a technician measures resistance between the brown and orange wires in that connector. A reading between 150 and 200 ohms indicates the defrost heater element itself is intact. Readings outside this range, or an open circuit, point to a broken heater element or a blown thermal fuse in series with the heater circuit. Short-circuit conditions will show near-zero resistance and indicate insulation breakdown or a wiring fault.

Beyond the heater element, the error can also be triggered by contact failures at connectors, a missing or improperly seated sensor housing, or a defective thermal fuse that has opened permanently rather than resetting. Even if the heater measures within spec, a faulty defrost sensor may be misreporting temperatures to the PCB, causing the board to terminate or mismanage the defrost cycle. Thorough diagnosis requires checking each component in the circuit individually before replacing the PCB.

Source: manufacturer service documentation.

Common causes of F-DEFROSTING ERROR

  1. 01

    Defrost heater element failure

    Part replacement

    The heater element itself may be open or broken. Disconnect CN70 from the Main PCB and measure resistance between the brown and orange wires; a reading outside 150 to 200 ohms confirms a failed heater.

  2. 02

    Blown or defective thermal fuse

    Part replacement

    The thermal fuse in the defrost circuit is designed to open if temperatures exceed safe limits. A permanently open fuse breaks the circuit and prevents any heating, showing as infinite resistance during the CN70 resistance check.

  3. 03

    Wiring damage or contact failure

    Wiring / connection

    Broken wires, corroded terminals, or loose connectors in the defrost heater circuit can interrupt current flow or cause intermittent shorts. Inspect the CN70 connector and the full wire harness from the PCB to the heater for visible damage or poor seating.

  4. 04

    Missing or improperly seated sensor housing

    Part replacement

    If the defrost sensor housing is absent or not correctly positioned, the sensor may read inaccurate temperatures and prevent the defrost cycle from completing within the 80-minute window.

  5. 05

    Defective defrost temperature sensor

    Part replacement

    A faulty sensor can send incorrect temperature data to the Main PCB, causing the control board to mismanage the defrost cycle even when the heater element is functioning correctly.

See the test procedure for each cause

Frequently asked questions about F-DEFROSTING ERROR

What does F-DEFROSTING ERROR mean on a LG refrigerator?
The F-DEFROSTING ERROR means the refrigerator's F compartment defrost cycle did not complete within 80 minutes of continuous heater operation. The control board monitors the defrost circuit and triggers this code when it detects a heater wire cut, short-circuit, contact failure, missing sensor housing, or a blown thermal fuse. The error identifies a breakdown somewhere in the defrost heater circuit that is preventing proper frost removal.
Can I fix the F-DEFROSTING ERROR myself?
Some causes, such as a loose connector or improperly seated sensor housing, can be addressed without replacing parts. However, confirming the root cause requires disconnecting the Main PCB CN70 connector and measuring resistance between the brown and orange wires to check for heater continuity. Replacing a heater element, thermal fuse, or defrost sensor involves accessing the interior panels of the freezer compartment, which is manageable for experienced DIYers but may be better left to a technician if you are unfamiliar with appliance wiring.
Will resetting the refrigerator clear the F-DEFROSTING ERROR?
A power reset may temporarily clear the error code from the display, but it will not resolve the underlying fault. If the heater element is broken, the thermal fuse is blown, or there is a wiring fault, the error will return once the refrigerator attempts its next defrost cycle. The root cause must be diagnosed and repaired to permanently clear the code.
Is the F-DEFROSTING ERROR a safety concern?
The error itself is not an immediate safety hazard, but leaving it unaddressed can cause significant frost buildup inside the freezer compartment. Excessive ice accumulation can block airflow, reduce cooling efficiency, and put added strain on the compressor. A shorted heater circuit can also pose a risk if wiring insulation is compromised, so it is advisable to have the circuit inspected promptly.
How much does it cost to repair the F-DEFROSTING ERROR on an LG refrigerator?
Repair costs vary depending on which component has failed. A thermal fuse is typically the least expensive fix, with parts generally ranging from a few dollars to around 20 dollars, plus labor. A defrost heater element replacement usually costs between 30 and 80 dollars for the part. If the Main PCB is involved, costs can rise to 100 to 300 dollars or more for parts alone. Adding professional labor typically brings total repair costs to the range of 100 to 400 dollars depending on the diagnosis.

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