mypros+
Error code reference

LG Refrigerator Error Code F3+F5

Poor defrosting at middle compartment

LG codesLG refrigerator codes

Poor defrosting at middle compartment - defrost sensor did not reach above 16°C within 2 hours after starting defrost.

First step from the service manual

Check temperature fuse, heater continuity, drain for clogging, and heater driving relay.

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

MyPros+ Max

Get the full diagnostic procedure for F3+F5.

  • 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
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What F3+F5 means on a LG refrigerator

The F3+F5 error code on an LG refrigerator indicates a defrost failure in the middle compartment. Specifically, the defrost sensor failed to reach a temperature above 16°C within a 2-hour defrost cycle window. This means the refrigerator's control board initiated a defrost sequence, monitored the sensor reading throughout the cycle, and determined that the heating element did not warm the evaporator sufficiently. The middle compartment evaporator relies on a dedicated defrost heater, a defrost sensor, and a thermal cutout (temperature fuse) working together to clear frost buildup on schedule.

When this code appears, the most likely hardware failures involve the defrost heater losing continuity, the temperature fuse blowing open due to overheating or age, or the heater driving relay on the control board failing to properly energize the heater circuit. A clogged or frozen drain can also contribute by causing ice to accumulate faster than normal and insulating the evaporator coils, preventing the sensor from reaching the target threshold even when the heater is functioning. Over time, a partially obstructed drain forces the defrost system to work harder, accelerating component wear.

Diagnosing this code requires checking heater continuity with a multimeter, inspecting the thermal fuse for continuity, clearing any drain blockage, and verifying that the heater relay on the main control board is switching correctly under load. A failed relay will prevent current from reaching the heater entirely even if the heater and fuse test good. All four of these components should be evaluated before replacing any single part.

Source: manufacturer service documentation.

Common causes of F3+F5

  1. 01

    Failed Defrost Heater

    Part replacement

    The defrost heater in the middle compartment may have lost continuity and is no longer generating heat. Use a multimeter to check resistance across the heater terminals; an open circuit reading confirms the heater needs replacement.

  2. 02

    Blown Temperature Fuse

    Part replacement

    The thermal cutout fuse is a safety device that opens permanently if it is exposed to excessive heat. Check it for continuity with a multimeter; no continuity means the fuse has blown and must be replaced.

  3. 03

    Failed Heater Driving Relay

    Part replacement

    The relay on the main control board is responsible for sending power to the defrost heater. If the relay contacts are burnt or stuck open, the heater will receive no power even if it tests good on its own.

  4. 04

    Clogged or Frozen Defrost Drain

    Wiring / connection

    A blocked drain allows meltwater to refreeze and build up around the evaporator, insulating the coils and preventing the sensor from reaching 16°C within the 2-hour window. Inspect the drain tube and drain pan for ice or debris blockage.

  5. 05

    Faulty Defrost Sensor

    Part replacement

    If the defrost sensor is reading temperatures inaccurately, the control board may log a failure even when the heater is operating correctly. Verify the sensor output matches expected values at known temperatures.

See the test procedure for each cause

Frequently asked questions about F3+F5

What does F3+F5 mean on a LG refrigerator?
The F3+F5 code means the middle compartment defrost sensor did not reach above 16°C within 2 hours after a defrost cycle started. This points to a problem in the middle compartment defrost system, which includes the heater, temperature fuse, defrost sensor, and the heater relay on the control board. The refrigerator uses this 2-hour window as a benchmark to confirm that defrosting is occurring properly. If frost accumulates unchecked, cooling performance in that section will eventually decline.
Can I fix the F3+F5 error myself?
Some steps, like clearing a clogged defrost drain, are within reach for a confident DIYer. However, testing heater continuity, checking the temperature fuse, and evaluating the control board relay require a multimeter and basic electrical safety knowledge. Replacing a defrost heater or thermal fuse involves accessing internal refrigerator components, which is manageable but does require unplugging the unit and partial disassembly. If you are not comfortable working with electrical components, a qualified technician is the safer choice.
Is the F3+F5 error code dangerous?
The error itself does not indicate an immediate safety hazard, but it should not be ignored. A failed defrost system will allow frost to accumulate on the evaporator coils, which reduces cooling efficiency and can eventually block airflow entirely. In some cases, a shorted heater or failed fuse can point to an underlying electrical issue that warrants prompt attention. Addressing the error code promptly prevents food spoilage and further component damage.
How much does it cost to repair the F3+F5 error on an LG refrigerator?
Repair costs vary depending on which component has failed. A defrost heater or thermal fuse typically costs between $15 and $60 for the part alone. If the main control board relay has failed and the board requires replacement, parts can range from $80 to $250 or more. Adding a technician's labor fee generally brings the total repair cost to somewhere between $100 and $400, depending on your location and the specific diagnosis.
Will resetting the refrigerator clear the F3+F5 error code?
A power reset may temporarily clear the code from the display, but it will not fix the underlying hardware fault. If the defrost heater, thermal fuse, or relay has failed, the defrost cycle will fail again and the code will return. A reset is only useful for ruling out a one-time control glitch. Proper diagnosis of the heater, fuse, drain, and relay should be completed to ensure the fault is genuinely resolved.

Related LG refrigerator codes

All LG refrigerator codes
View all 485 LG refrigerator codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass