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Error code reference

LG Refrigerator Error Code Freezer Defrost Function Error

Defrost system in FZ compartment has errors (heater, bimetal, or temperature fuse failure; defrost mode…

LG codesLG refrigerator codes

Defrost system in FZ compartment has errors (heater, bimetal, or temperature fuse failure; defrost mode finished due to 70-minute time limit).

First step from the service manual

After separating MAIN PCB CN70,CN71 from PCB, measure resistance between CN70 brown <-> CN71 Orange: shall be 55(220) ohm +/- 7%.

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

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What Freezer Defrost Function Error means on a LG refrigerator

The Freezer Defrost Function Error on an LG refrigerator indicates a fault within the defrost system of the freezer compartment. This error triggers when the control board detects that the defrost cycle either failed to complete correctly or was forced to terminate after reaching the maximum allowed run time of 70 minutes. The defrost system relies on three key components working in sequence: the defrost heater, which melts frost buildup off the evaporator coils; the bimetal thermostat, which acts as a safety cutoff once the coils reach a target temperature; and the thermal fuse, which provides a one-time overheat protection. A failure in any one of these components can cause the error to appear.

Diagnosing this error begins at the main PCB connectors CN70 and CN71. After disconnecting these connectors from the PCB, a technician measures resistance between the brown wire on CN70 and the orange wire on CN71. The expected resistance is 55 ohms for 220-volt models, with an acceptable tolerance of plus or minus 7%. A reading outside this range indicates an open or failed component in the defrost circuit, such as a blown thermal fuse or a failed heater element. A resistance reading of infinite or open-circuit strongly suggests a thermal fuse or heater failure, while a reading that is significantly lower than spec may point to a shorted component.

If the resistance checks within specification but the error still appears, the bimetal thermostat may be sticking open or the defrost cycle duration is consistently exceeding the 70-minute cutoff, which suggests excessive frost accumulation due to a door seal leak, a faulty defrost termination thermostat, or an issue with defrost cycle initiation timing on the control board itself.

Source: manufacturer service documentation.

Common causes of Freezer Defrost Function Error

  1. 01

    Blown Thermal Fuse

    Part replacement

    The thermal fuse is a one-time safety device that fails permanently if the defrost heater overheats. A blown fuse will show as an open circuit (infinite resistance) when measuring between CN70 brown and CN71 orange, confirming the failure.

  2. 02

    Failed Defrost Heater

    Part replacement

    The defrost heater element can burn out or break, preventing frost from melting off the evaporator coils. This will produce a resistance reading outside the expected 55 ohm range (plus or minus 7%) when tested at the CN70 and CN71 connectors.

  3. 03

    Faulty Bimetal Thermostat

    Part replacement

    The bimetal thermostat cuts power to the heater once the evaporator reaches the target temperature. If it sticks open, it interrupts the defrost circuit before the cycle completes, triggering the error.

  4. 04

    Defrost Cycle Exceeding 70-Minute Time Limit

    Wiring / connection

    If frost accumulation is excessive due to a worn door gasket or frequent door opening, the defrost cycle cannot complete within the 70-minute limit and the board flags an error. Inspecting the door seals and usage habits can help identify this cause.

  5. 05

    Wiring or Connector Issue

    Wiring / connection

    Loose, corroded, or damaged wiring between CN70, CN71, and the defrost components can interrupt the circuit and produce an out-of-range resistance reading even if the heater, fuse, and bimetal are individually intact.

See the test procedure for each cause

Frequently asked questions about Freezer Defrost Function Error

What does Freezer Defrost Function Error mean on a LG refrigerator?
This error means the defrost system in the freezer compartment has a detected fault. The control board has determined that the defrost heater, bimetal thermostat, or thermal fuse has failed, or that the defrost cycle ran for the full 70-minute maximum without completing successfully. Left unaddressed, frost will accumulate on the evaporator coils and reduce the refrigerator's ability to cool properly.
Can I fix the Freezer Defrost Function Error myself?
A knowledgeable DIYer can perform the resistance test at connectors CN70 and CN71 with a multimeter to identify whether the heater, thermal fuse, or bimetal thermostat has failed. Replacing those components is a manageable repair if you are comfortable working inside a refrigerator and disconnecting electrical connectors. However, if the wiring or main PCB is involved, professional service is recommended.
Is it safe to keep using my refrigerator while this error is active?
Continued use with an active defrost error is not ideal, as frost buildup on the evaporator coils will progressively reduce cooling efficiency in both the freezer and fresh food compartments. Food safety can become a concern if temperatures rise above safe thresholds. It is best to address the error promptly rather than continuing to operate the appliance without repair.
How much does it cost to repair a Freezer Defrost Function Error on an LG refrigerator?
Repair costs vary depending on which component has failed. A thermal fuse or bimetal thermostat are relatively inexpensive parts, typically in the range of $5 to $30 each, though labor costs will add to the total if a technician is hired. A defrost heater assembly may cost between $20 and $80 in parts. If the main PCB is at fault, costs can range from $100 to $300 or more for parts alone.
Will resetting the refrigerator clear the Freezer Defrost Function Error?
Resetting the refrigerator by unplugging it may temporarily clear the error code from the display, but the underlying defrost system fault will remain. If the heater, thermal fuse, or bimetal thermostat has failed, the error will return once the control board runs the next defrost cycle and detects the problem again. A proper repair of the failed component is required to permanently resolve the error.

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