March 13, 2026

If your LG air conditioner has visible frost or ice on the evaporator coil, water pooling beneath the unit, or suddenly weak airflow with poor cooling, the coil is freezing. This should never happen during normal operation. Coil freezing has two root causes: restricted airflow that starves the coil of warm air, or a refrigerant problem that makes the coil too cold regardless of airflow. This guide covers every cause and gives you step-by-step fixes for each one.

Before You Fix Anything: Thaw the Coil First

How to Safely Thaw a Frozen LG AC Coil

1. Turn the unit off at the power button and unplug it from the wall.

2. If your model has Fan Only mode, plug it back in and run fan only. This speeds up the thaw. Do not select Cool mode. Without Fan Only, leave unplugged and allow 2 to 4 hours to thaw at room temperature.

3. Place towels beneath the unit to catch dripping meltwater.

4. Do not chip or scrape ice off the coil. This bends the aluminum fins and can puncture the refrigerant tubing.

All Causes at a Glance

Cause 1: Clogged Air Filter

A blocked filter is the most common cause. It restricts warm airflow over the coil, dropping its temperature below freezing. LG recommends cleaning the filter every two weeks.

How to Fix LG AC Coil Freezing Caused by a Clogged Filter

1. After thawing the coil, unplug the unit.

2. Remove the front panel, slide out the filter, and hold it up to a light. If light barely passes through, it is clogged.

3. Rinse under lukewarm water with a soft brush and allow to air dry completely before reinstalling.

4. Reinstall the dry filter, restore power, and run in Cool mode for 30 minutes to confirm the coil stays clear.

Cause 2: Dirty Evaporator Coil

Fine dust settles on the coil fins and acts as insulation, preventing proper heat absorption. The coil drops below freezing even when the filter is clean.

How to Fix LG AC Coil Freezing Caused by a Dirty Evaporator Coil

1. After thawing the coil, unplug the unit.

2. Remove the front panel and filter. Inspect the coil with a flashlight for visible grey or brown residue on the fins.

3. Apply a no-rinse foaming AC coil cleaner onto the coil and follow the product directions for dwell time.

4. Allow the foam to drain. For heavier buildup, use a soft coil brush in the direction of the fins only.

5. Allow the coil to dry fully, reassemble, restore power, and monitor for 30 minutes.

Cause 3: Dirty Blower Wheel

Dust packed into the blower wheel fins reduces the volume of air pushed across the coil. The fan appears to spin normally but airflow is a fraction of what it should be.

How to Fix LG AC Coil Freezing Caused by a Dirty Blower Wheel

1. After thawing the coil, unplug the unit.

2. Remove the front panel and filter. Shine a flashlight at the blower wheel and look for buildup packed into the fin blades.

3. Use a stiff brush and coil cleaner spray to work dust out of the fins, then follow with compressed air.

4. Reassemble and restore power. Confirm airflow from the vents is noticeably stronger.

Cause 4: Thermostat Set Too Low

Running the unit at its lowest temperature setting forces the coil to work continuously at near-maximum capacity. The surface drops below freezing and moisture ices over on contact, especially overnight when room temperatures are already low.

How to Fix LG AC Coil Freezing Caused by a Low Temperature Setting

1. After thawing the coil, raise the set temperature. LG recommends not going below 65 degrees Fahrenheit in normal residential use.

2. Use Auto fan mode if available. This reduces compressor output as the room nears the target temperature and lowers the risk of the coil getting too cold.

3. Run the unit at the adjusted setting and monitor for 30 minutes to confirm the coil stays clear.

Cause 5: Blocked Vents or Obstructed Intake

Objects blocking the intake or discharge grilles cut off the warm air supply to the coil. On portable LG units, a kinked or too-long exhaust hose also creates back pressure that disrupts airflow.

How to Fix LG AC Coil Freezing Caused by Blocked Vents

1. After thawing the coil, turn the unit off and unplug it.

2. Move any furniture, curtains, or objects within two feet of the intake or discharge grilles.

3. On portable units, straighten the exhaust hose, shorten it if needed, and confirm the window seal is tight.

4. Restore power and run the unit. Monitor for 30 minutes to confirm the coil stays clear.

Cause 6: Faulty Blower Motor

A failing motor runs below rated speed, moving less air than the coil needs to stay above freezing. It may also slow down as it heats up during operation.

How to Fix LG AC Coil Freezing Caused by a Faulty Blower Motor

1. After thawing, unplug the unit and spin the blower wheel by hand. It should rotate freely. Drag or grinding indicates bearing failure.

2. Test the motor windings with a multimeter in resistance mode. An open circuit means the blower motor has failed. Also test the capacitor in capacitance mode and compare to the rated value on the body.

3. Replace the faulty component with a genuine OEM LG part for your model number. Confirm strong airflow before running in Cool mode.

Cause 7: Low Refrigerant Charge

A refrigerant leak drops coil pressure, causing refrigerant to absorb heat at a far lower temperature than designed. Unlike airflow-related freezing, this typically produces ice in one localised coil section and is accompanied by a hissing sound and reduced cooling performance.

How to Fix LG AC Coil Freezing Caused by Low Refrigerant

1. Turn the unit off and allow the coil to fully thaw.

2. Do not attempt to add refrigerant yourself. This is regulated by law and requires an EPA-certified HVAC technician.

3. Contact a certified HVAC technician to locate and seal the leak and recharge the system.

4. Do not run the unit in Cool mode while refrigerant is low. This can cause permanent compressor failure.

Cause 8: Faulty Expansion Valve

If the expansion valve sticks open, too much refrigerant floods the coil at once and drives the surface temperature far below freezing even with normal airflow. This is diagnosed after ruling out all airflow causes.

How to Fix LG AC Coil Freezing Caused by a Faulty Expansion Valve

1. Thaw the coil and clean the filter, evaporator coil, and blower wheel thoroughly first. If the coil still freezes after all that, proceed.

2. Contact a certified HVAC technician. Expansion valve replacement requires access to the sealed refrigerant system and is not a DIY repair.