If your LG refrigerator is showing Er FS, it usually means the freezer temperature sensor (also called the freezer thermistor) is reporting an abnormal reading or its circuit is interrupted. That can stop cooling, cause temperature fluctuations, or make the fridge display an error and stop certain functions. This page explains the fault, common causes, safe do-it-yourself checks, step-by-step home fixes, and practical prevention tips — written in plain American English so anyone can follow along.
Quick summary: what “Er FS” means
- Er FS = freezer sensor error (freezer thermistor or its circuit).
- Symptoms: freezer too warm or too cold, temperature readouts jump, compressor cycles irregularly, or error appears on the display.
- Typical reason: sensor reading out of range, open circuit, short, or wiring/connector problem between the sensor and control board.
- Easy first check: inspect wiring and test the sensor resistance with a multimeter (see diagnostic steps below).
Why this fault happens (in plain words)
The freezer sensor tells the refrigerator’s control board how cold the freezer is. If that information is wrong or missing, the control board can’t control defrost and compressor timing properly. A failing sensor will give inaccurate temperature readings. Wiring that’s corroded, pinched, or loose can interrupt the signal. Ice buildup around the sensor can also insulate it and create false readings. Less commonly, the control board itself can fail and misinterpret a perfectly good sensor.
Tools and parts you may need
- Digital multimeter (ohms / continuity).
- Phillips and flathead screwdrivers.
- Work gloves.
- Replacement freezer sensor (OEM or model-compatible thermistor) if the original fails testing.
- Needle-nose pliers (optional) for reaching clips or connectors.
How to safely diagnose and fix Er FS at home
Always unplug the refrigerator or switch off the breaker before doing any electrical checks. Wait for the compressor to be off and the interior to be cool enough to work in.
Start with a visual inspection. Open the freezer and locate the sensor — usually a small probe mounted on the back wall or inside the evaporator cover. Look for obvious signs: crushed or chewed wiring, corrosion at the connector, or a probe buried under ice.
Next, test the sensor with a multimeter. Pull the sensor connector free (don’t yank the wires) and measure resistance across the two sensor pins. Compare the reading to the value listed in your LG service manual for room temperature. Typical thermistor resistance varies by model, so if yours reads open (OL) or short (very low ohms) it’s faulty. If the resistance is within the expected range but the error remains, check the wiring harness for continuity from the sensor plug back to the control board connector. Wiggle the connector while watching the meter — intermittent changes indicate a loose pin or broken conductor.
If the sensor tests bad, replacing it is usually straightforward: remove the screws or clips holding it, unplug, swap in the new sensor, reattach the cover, restore power, and observe operation. If wiring is damaged, replacing the harness or splicing with proper connectors is needed. If sensor and wiring check out but Er FS persists, the control board input circuit may be failing — at that point professional diagnosis is recommended.
Practical, easy prevention tips
Keeping the sensor and surrounding area clean and ice-free prevents many false readings. Avoid blocking airflow inside the freezer with large items pressed against the back wall. Defrost the freezer if ice buildup is visible around the sensor or evaporator cover. During routine cleaning, inspect the sensor harness for wear or nicks and fix any small issues before they turn into electrical faults. Using a water filter and softener where water hardness is extreme won’t directly change the sensor but can help overall appliance longevity by reducing mineral deposits in the system.
Quick troubleshooting checklist
- Unplug the fridge or turn off the breaker before working on it.
- Locate the freezer sensor and visually inspect it and its wiring.
- Measure sensor resistance with a multimeter and compare to your model’s spec.
- Replace the sensor if it reads open, shorted, or out of range.
- Check harness continuity back to the control board; repair or replace damaged wiring.
- If sensor and wiring are fine but error persists, consider a control board fault and contact a qualified technician.
Final notes and what to expect
Replacing a faulty freezer sensor is one of the simpler refrigerator repairs and is often inexpensive. If you decide to replace the part yourself, match the exact part number or choose a recommended OEM substitute to avoid compatibility problems. If wiring or the control board is involved, or if you feel uncomfortable handling electrical components, booking a professional visit is the safest course. Fixing Er FS promptly keeps food safe and prevents bigger cooling or defrost issues down the road.