LG Refrigerator 1F Error Code: Freezer Defrost Sensor Fault

Quick Answer

The LG 1F error code means the freezer defrost temperature sensor has failed. Without a working sensor, the control board cannot monitor evaporator temperature or trigger defrost cycles. Ice builds up on the evaporator coils over days, eventually blocking all airflow and causing the refrigerator to warm up.

In my experience, this code usually pops up about three days after the actual failure once the ice buildup finally chokes out the airflow. You will notice the freezer stays cold while the fridge section starts warming up. It is almost always the defrost thermistor, a small plastic bulb clipped to the cooling coils. Replacing it is a straightforward DIY job that saves you a $300 service call for a $20 part.

LgRefrigeratorSeverity: highDifficulty: intermediate88% DIY Success

Time to Fix

30–60 min

Difficulty

intermediate

Parts Cost

$15 – $30

Tools Needed

Phillips screwdriver, Multimeter

What Does the 1F Code Mean?

When your LG shows 1F, the main control board has essentially gone blind to the evaporator temperature. It cannot tell if the coils are frosted or clear, so it skips the defrost cycle. I often see homeowners mistake this for an 'IF' fan error, but 1F is strictly a sensor communication breakdown.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Defrost sensor probe failed internally (most common)40%

Wiring harness to sensor chafed or corroded24%

Sensor connector pin backed out14%

Physical damage to sensor from ice impact12%

Control board defrost sensor circuit failed10%

Symptoms You May Notice

1F displayed on temperature panel
Freezer not reaching target temperature
Visible frost buildup on back wall of freezer
Fresh food compartment warming up over several days
Refrigerator running constantly without cycling off

Can you reset a Lg refrigerator to clear the 1F code?

You can clear the code by unplugging the unit or cycling the breaker for five minutes, but do not let that fool you. The LG logic board checks this sensor resistance constantly. If the thermistor is truly open or shorted, that 1F will stare back at you within an hour. Use this reset only to get the display back so you can run a manual test.

Tools Required for Diagnosis

Phillips screwdriverMultimeterPutty knife (for panel clips)Towels for ice/water

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name	OEM Number	Estimated Price
Freezer Defrost Temperature Sensor Assembly6615JB2002A · $15–$30	6615JB2002A	$15 – $30

Frequently Asked Questions

Can I run my LG refrigerator with a 1F error code showing?

You have a very short window before things get messy. While the fridge might feel okay for the first few hours, that 1F code means your defrost system is dead. Within 48 to 72 hours, the frost on the cooling coils will turn into a solid block of ice. Once that happens, the fan cannot pull air through the coils, and your milk will start spoiling in the fresh food section. I always tell my customers to move their perishables to a cooler immediately if they cannot fix this the same day.

What ohm reading should the LG defrost sensor show?

Resistance changes with temperature, so context matters. In a cold freezer around 0 degrees, you should see roughly 10,000 to 12,000 ohms. If you have had the doors open and the unit is closer to 32 degrees, look for about 6,000 ohms. At room temperature (70 degrees), it should drop to around 2,500 ohms. If your meter shows 'OL' or '1' (open loop), the internal thermistor wire has snapped. If it shows 0, it has shorted out. Both mean the sensor is garbage and needs to go.

Where exactly is the 1F sensor located inside the LG freezer?

You will find it hiding behind the rear interior panel of the freezer. After you clear out the shelves and unscrew the plastic cover, look at the top of the silver evaporator coils. The sensor is usually a small white or black plastic bulb, about an inch long, clipped directly onto the copper or aluminum tubing. It will have two wires leading to a plastic connector. Do not confuse it with the defrost heater, which is the long glass or metal tube at the bottom of the coils.

I replaced the 1F sensor but the code came back. What now?

This is rare but it does happen. If you have installed a brand new OEM sensor and the 1F code returns after a hard reset, you need to check the resistance at the main control board. If the resistance is correct at the board's wire harness but the code persists, the logic chip on the board is failing to read the data. At that point, you are looking at replacing the main PCB, which is usually located in a compartment on the back of the fridge.

Is the LG 1F error code the same as the dF error on other brands?

Actually, there is a big difference that trips people up. The 1F code specifically points to the freezer defrost sensor. However, many LG owners misread 'IF' as '1F' because of the digital display. The IF code actually indicates a problem with the ice fan. If you see this code, first confirm it is a '1' and not an 'I'. If it is definitely 1F, follow the defrost sensor testing steps. If it is IF, you are looking at a fan motor or ice buildup in the door duct.

Related Lg Refrigerator Error Codes

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Same Fix Works on These Brands

Lg shares the same hardware platform with these brands. The diagnosis and repair steps are identical.

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Models Known to Experience 1F Errors

This repair applies to most Lg refrigerators with this error code. Common model numbers include:

LRMVS3006S, LRFXS2503S, LRFXC2416S, LRMGS2806S, LSXS26366S

Written by

Mike Sullivan

Lead Appliance Repair Technician · 20 years experience

Last verified for technical accuracy on March 14, 2026