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Error code reference

LG Refrigerator Error Code R1 R2 R3 R4 (blinking pattern 3)

Defrost problem

LG codesLG refrigerator codes

Defrost problem - Defrost time exceeded 2 hours and evaporator temperature did not reach 13°C.

First step from the service manual

Check defrost heater, defrost sensor, thermal fuse, and heater relay (RY5 on Main PWB).

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 R1 R2 R3 R4 (blinking pattern 3) means on a LG refrigerator

The R1 R2 R3 R4 blinking pattern 3 error on LG refrigerators indicates a defrost system failure. Specifically, the control board has logged that the automatic defrost cycle ran for more than 2 hours without the evaporator temperature climbing to the minimum threshold of 13°C. Under normal operation, the defrost heater warms the evaporator coil to melt accumulated frost within a set time window. When the system cannot reach that target temperature, the board flags the fault and displays this blinking pattern to alert the technician that the defrost circuit is not functioning correctly.

The defrost system involves several components working in sequence. The main PWB initiates the defrost cycle by energizing heater relay RY5, which closes the circuit to the defrost heater. A defrost sensor monitors evaporator temperature throughout the cycle, and a thermal fuse provides a one-time overtemperature cutoff as a safety backup. If any of these components fail, whether an open-circuit heater, a failed sensor sending incorrect temperature readings, a blown thermal fuse, or a defective RY5 relay that never fully closes, the heater either never activates or produces insufficient heat to reach 13°C within the 2-hour window.

Ice buildup on the evaporator coil is a direct consequence of a failed defrost cycle. Over time, restricted airflow from a frost-blocked evaporator will cause the refrigerator and freezer compartments to warm up. Because the fault must accumulate over time before the board trips the error, some frost accumulation is typically already present when this code appears. Addressing all suspect components in the defrost circuit is essential before clearing the fault and returning the unit to service.

Source: manufacturer service documentation.

Common causes of R1 R2 R3 R4 (blinking pattern 3)

  1. 01

    Blown thermal fuse

    Part replacement

    The thermal fuse is a one-time safety device that permanently opens if the defrost heater area overheats. A blown fuse breaks the defrost circuit entirely, preventing the heater from activating. Test for continuity across the fuse terminals to confirm.

  2. 02

    Failed defrost heater

    Part replacement

    An open or shorted defrost heater cannot generate heat to melt frost off the evaporator coil. Disconnect the heater and measure resistance across its terminals; an open circuit reading indicates the heater has failed and must be replaced.

  3. 03

    Defective heater relay RY5 on the main PWB

    Part replacement

    Relay RY5 on the main control board is responsible for switching power to the defrost heater. If the relay contacts are welded open or the coil has failed, the heater never receives power even when the board initiates a defrost cycle. Inspect and test the relay or replace the main PWB if the relay is integrated.

  4. 04

    Faulty defrost sensor

    Part replacement

    The defrost sensor monitors evaporator temperature and signals the control board during the defrost cycle. If the sensor is reading temperatures incorrectly, the board may terminate the cycle early or receive inaccurate data, triggering the 2-hour timeout fault.

  5. 05

    Heavy frost accumulation blocking the evaporator

    Wiring / connection

    In some cases, an extreme buildup of ice on the evaporator coil from prior failed defrost cycles can make it physically impossible for a functioning heater to reach 13°C within 2 hours. Manual defrosting the unit first can help isolate whether the fault is a component failure or a backlog of ice.

See the test procedure for each cause

Frequently asked questions about R1 R2 R3 R4 (blinking pattern 3)

What does R1 R2 R3 R4 (blinking pattern 3) mean on a LG refrigerator?
This blinking pattern indicates a defrost system fault. The refrigerator's control board detected that the defrost cycle ran for more than 2 hours without the evaporator temperature reaching 13°C. This points to a failure in one or more components of the defrost circuit, including the defrost heater, thermal fuse, defrost sensor, or heater relay RY5 on the main control board.
Can I fix the R1 R2 R3 R4 blinking pattern 3 error myself?
Some steps, such as manually defrosting the unit by unplugging it and allowing ice to melt, can be done without specialized tools. However, fully diagnosing the fault requires testing the defrost heater for continuity, checking the thermal fuse, verifying the defrost sensor, and inspecting relay RY5 on the main PWB. These steps involve working with electrical components inside the freezer compartment and are best handled by someone with appliance repair experience and a multimeter.
Will resetting the refrigerator clear this error code?
Resetting the refrigerator by unplugging it may temporarily clear the displayed fault, but the error will return as soon as the next defrost cycle fails to meet the 13°C threshold within 2 hours. The underlying cause in the defrost circuit must be repaired before the error will stay cleared. Resetting without repair is not a solution.
Is it safe to keep using my LG refrigerator while this error is active?
Continuing to run the refrigerator with an active defrost fault is not recommended. Frost will continue to accumulate on the evaporator coil, progressively restricting airflow and reducing cooling performance in both compartments. Over time, food safety can be compromised as temperatures rise. The unit should be diagnosed and repaired promptly.
How much does it cost to repair the R1 R2 R3 R4 blinking pattern 3 error on a LG refrigerator?
Repair costs vary depending on which component has failed. Replacing a thermal fuse or defrost sensor is generally inexpensive, with parts typically ranging from $10 to $40 and labor adding $80 to $150 depending on your area. A defrost heater replacement may run $30 to $80 in parts. If the main control board needs replacement due to a failed RY5 relay, costs can range from $150 to $350 or more for parts and labor combined.

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