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Error code reference

LG Refrigerator Error Code FD

Freezer defrost sensor disconnection or short circuit (displays 'Lo' for disconnection, 'Hi' for short).

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Freezer defrost sensor disconnection or short circuit (displays 'Lo' for disconnection, 'Hi' for short).

First step from the service manual

Measure the resistance between both terminals after separating CN15 of the Main PCB. If FD-sensor is disconnected or shorted, change the FD-sensor on the evaporator.

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

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What FD means on a LG refrigerator

The FD error code on an LG refrigerator indicates a fault with the freezer defrost sensor, also called the FD sensor, located on the evaporator. This sensor monitors temperature during the defrost cycle to regulate timing and prevent overheating. The code distinguishes between two specific fault states: when the display reads 'Lo' alongside FD, the sensor circuit is open (disconnected), meaning continuity has been lost. When the display reads 'Hi', the sensor has short-circuited, causing an abnormally low resistance reading. Both conditions prevent the control board from receiving accurate temperature data from the evaporator.

The primary diagnostic step involves isolating the sensor from the main control board by disconnecting connector CN15 on the Main PCB, then measuring resistance across both sensor terminals with a multimeter. A properly functioning defrost sensor will return a resistance value within its rated range. An open circuit reading indicates a broken wire, failed sensor element, or disconnected harness. A reading near zero ohms confirms a short circuit within the sensor itself or in the wiring between the sensor and the board.

Common causes include physical damage to the sensor from ice buildup pressing against the harness, connector corrosion at CN15, and simple sensor element failure from age or repeated thermal cycling. Because the defrost sensor directly controls the safety shutoff of the defrost heater, a faulty reading can lead to under-defrosting or uncontrolled heater operation, both of which affect cooling performance and can cause secondary component damage if left unaddressed.

Source: manufacturer service documentation.

Common causes of FD

  1. 01

    Failed FD sensor element

    Part replacement

    The sensor element itself degrades over time due to thermal cycling, causing it to read as an open circuit ('Lo') or short circuit ('Hi'). This is the most frequent root cause and is confirmed by measuring resistance directly at the sensor terminals after disconnecting CN15.

  2. 02

    Disconnected or damaged sensor harness

    Wiring / connection

    The wiring harness connecting the FD sensor to CN15 on the Main PCB can become pinched, cracked, or pulled loose, breaking the circuit and triggering the 'Lo' disconnection error. Inspect the full length of the harness for visible damage or loose connector seating.

  3. 03

    Corrosion or damage at CN15 connector

    Wiring / connection

    The CN15 connector on the Main PCB can develop corrosion or bent pins from moisture exposure inside the freezer compartment, causing an intermittent or permanent open circuit. Visually inspect the connector terminals for oxidation or physical deformation.

  4. 04

    Ice buildup pressing on sensor wiring

    Wiring / connection

    Excessive frost accumulation on the evaporator can physically compress or pull on the sensor wiring, stressing the connection points or the sensor body itself. This is more likely if the defrost system has had prior issues or if the unit has gone extended periods without completing a proper defrost cycle.

  5. 05

    Main PCB fault

    Part replacement

    In rare cases, the Main PCB circuit associated with CN15 may fail, causing it to misread a functioning sensor as disconnected or shorted. This should only be considered after the sensor and harness have been tested and confirmed good.

See the test procedure for each cause

Frequently asked questions about FD

What does FD mean on a LG refrigerator?
The FD error code indicates a problem with the freezer defrost sensor located on the evaporator. If the display shows 'Lo' with the FD code, the sensor circuit is open or disconnected. If it shows 'Hi', the sensor has short-circuited. In both cases, the refrigerator cannot accurately monitor evaporator temperature during the defrost cycle.
Can I fix the FD error code myself?
A knowledgeable DIYer can perform the resistance check by disconnecting connector CN15 on the Main PCB and measuring across the sensor terminals with a multimeter. If the sensor reads as open or shorted, the FD sensor on the evaporator needs to be replaced. Accessing the evaporator requires removing freezer shelving and the rear panel, which is manageable but does involve working around electrical components and refrigerant lines.
Will resetting my LG refrigerator clear the FD error?
A power reset may temporarily clear the FD error from the display, but the code will return if the underlying sensor fault is still present. The sensor circuit must be tested and the faulty component replaced to permanently resolve the error. Repeated resets without repair will not restore proper defrost function.
Is it safe to keep using my refrigerator while the FD code is active?
Operating the refrigerator with an active FD error is not recommended for extended periods. Without a functioning defrost sensor, the defrost cycle cannot be properly controlled, which can lead to excessive frost buildup on the evaporator, reduced cooling performance, and potential strain on other components. Food safety may be affected if cooling becomes inadequate.
How much does it cost to repair an FD error on an LG refrigerator?
If the FD sensor itself needs replacement, parts typically range from roughly $15 to $50 depending on the specific model. If a professional technician is needed for diagnosis and replacement, total repair costs including labor generally range from $100 to $250. Costs can be higher if the Main PCB is found to be faulty instead of the sensor.

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