mypros+
Error code reference

LG Refrigerator Error Code Er 4

Abnormal defrost sensor

LG codesLG refrigerator codes

Abnormal defrost sensor - short circuit of defrost heater, temperature fuse, or unplugged connector (displays 4 hours after fault occurs).

First step from the service manual

Check defrost sensor and heater connections; check temperature fuse continuity.

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 Er 4.

  • 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 Er 4 means on a LG refrigerator

The Er 4 error code on an LG refrigerator indicates an abnormal condition in the defrost sensor circuit. Specifically, the control board has detected a short circuit or open circuit condition involving the defrost heater, the thermal (temperature) fuse, or a disconnected wiring connector in the defrost system. Because the refrigerator waits to confirm the fault is persistent rather than transient, this code does not display immediately. It appears approximately 4 hours after the fault is first detected.

The defrost system relies on several components working together: a defrost heater to melt frost off the evaporator coils, a defrost sensor (thermistor) to monitor temperature during the defrost cycle, and a thermal fuse that acts as a safety cutoff if temperatures exceed a safe threshold. A short circuit in the heater, a blown thermal fuse, or a loose or unplugged wiring connector can all interrupt the circuit in a way the control board interprets as an abnormal defrost sensor reading.

Diagnosis should begin with a visual inspection of all connectors in the defrost circuit, followed by continuity testing of the thermal fuse and resistance testing of the defrost heater and sensor. A blown thermal fuse will show no continuity and must be replaced. A defrost heater with a shorted or open element will similarly require replacement. If connectors are simply loose or corroded, reseating or cleaning them may resolve the fault without further parts replacement.

Source: manufacturer service documentation.

Common causes of Er 4

  1. 01

    Blown thermal fuse

    Part replacement

    The thermal fuse is a one-time safety device that opens permanently if the defrost system overheats. Testing with a multimeter will show no continuity across a blown fuse, confirming it needs replacement.

  2. 02

    Unplugged or loose wiring connector

    Wiring / connection

    Connectors in the defrost circuit can vibrate loose or become unseated over time. A visual inspection of the wiring harness connections at the defrost heater, sensor, and thermal fuse should be performed first.

  3. 03

    Failed defrost heater

    Part replacement

    A short circuit or open element in the defrost heater will disrupt the circuit and trigger this code. Resistance testing of the heater terminals can confirm whether the element has failed.

  4. 04

    Defective defrost sensor (thermistor)

    Part replacement

    If the defrost sensor itself has shorted internally, the control board will register an abnormal reading in the defrost circuit. The sensor should be tested for proper resistance values at a known temperature.

  5. 05

    Corroded or damaged wiring

    Wiring / connection

    Moisture inside the freezer compartment can cause corrosion at connector terminals or damage wire insulation, creating intermittent or permanent faults in the defrost circuit.

See the test procedure for each cause

Frequently asked questions about Er 4

What does Er 4 mean on a LG refrigerator?
Er 4 indicates an abnormal defrost sensor condition caused by a short circuit in the defrost heater, a blown thermal fuse, or a disconnected wiring connector in the defrost circuit. The code does not appear immediately; it displays approximately 4 hours after the fault is first detected by the control board. This error means the defrost system is not functioning correctly and requires inspection.
Can I fix Er 4 on my LG refrigerator myself?
Some causes of Er 4, such as a loose or unplugged wiring connector, can be resolved without replacing any parts if you are comfortable working inside the freezer compartment. However, replacing a blown thermal fuse or a failed defrost heater requires purchasing the correct replacement component and basic skills with a multimeter for continuity and resistance testing. If you are not comfortable with electrical testing, a qualified appliance repair technician should perform the diagnosis.
Is it safe to keep using my LG refrigerator when Er 4 is showing?
A refrigerator displaying Er 4 has a non-functional defrost system, which means frost will continue to accumulate on the evaporator coils. Over time, this will restrict airflow and cause the refrigerator to lose cooling ability. While the appliance may continue running in the short term, leaving the fault unrepaired risks food spoilage and potential compressor strain. Addressing the error promptly is recommended.
Will resetting my LG refrigerator clear the Er 4 code?
A power reset may temporarily clear the Er 4 display, but the code will return within approximately 4 hours if the underlying fault in the defrost circuit has not been corrected. Because the error is tied to a hardware fault such as a blown fuse, a failed heater, or a loose connector, resetting alone does not constitute a repair. The root cause must be identified and corrected.
How much does it cost to repair Er 4 on an LG refrigerator?
Repair costs vary depending on which component has failed. A thermal fuse is typically an inexpensive part, often in the range of $5 to $20, while a defrost heater assembly can cost $20 to $80 or more depending on the model. If you hire a technician, labor charges will add to the total, generally bringing the full repair cost to somewhere between $100 and $300 depending on your location and the specific parts needed.

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