LG Refrigerator Error Code R1 R2 R3 R4 (blinking pattern 2)

This blinking pattern indicates a faulty defrost sensor, also called the D sensor. The sensor circuit is either open or short-circuited, which prevents the refrigerator from receiving valid temperature data during the defrost cycle. As a result, the automatic defrost function is disabled until the fault is corrected. Voltage at the sensor circuit test point will read either 0V for a short circuit or 5V for an open circuit, compared to the normal operating range of 0.5V to 4.5V.

The refrigerator will continue to cool in the short term, but with defrost disabled, frost will accumulate on the evaporator coil over time. As frost builds up, airflow is restricted and cooling performance will decrease, potentially leading to food spoilage. It is best to address this fault promptly rather than continuing to run the unit in a degraded state.

A power reset may temporarily clear the error code from the display, but it will return as soon as the control board attempts to read the defrost sensor again and detects the same open or short-circuit condition. The fault code will continue to appear until the underlying hardware problem, whether the sensor, wiring, or connector, is actually repaired or replaced.

A knowledgeable DIYer can test the defrost sensor using a multimeter to check voltage at Point B in the sensor circuit and measure resistance at the sensor terminals. If the wiring harness and connector check out correctly and the sensor readings are out of range, replacing the defrost sensor is a manageable repair. However, if the fault lies in the wiring harness or control board, the repair is more involved and may benefit from professional service.

If only the defrost sensor needs replacement, parts typically cost in the range of $15 to $60 depending on the specific model, making it one of the more affordable refrigerator repairs. If professional labor is involved, total repair costs can range from $100 to $250 or more depending on local rates and the extent of any additional wiring or component damage found during diagnosis.