LG makes some of the most energy-efficient and technologically advanced air conditioners on the market, from compact window units to full inverter split systems with ThinQ smart home integration. But like any air conditioning brand, LG units develop predictable problems over time, and knowing what’s actually causing an issue makes the difference between a five-minute DIY fix and an unnecessary service call.
This guide covers every common LG air conditioner problem, what’s causing it, what you can fix yourself, and what the error codes on your display actually mean.
Problem 1: LG Air Conditioner Not Cooling
Not cooling as expected is the most common complaint from LG AC users. Before assuming a hardware fault, work through this checklist in order, since the majority of “not cooling” complaints come down to one of these fixable causes rather than a failed component.
Check the air filter first, every time.
A clogged air filter is the single most common cause of reduced cooling across every AC brand, not just LG. When the filter is blocked with dust and debris, airflow over the evaporator coil drops significantly, the coil can’t absorb heat properly, and the room simply won’t cool to the set temperature regardless of how low you set the thermostat. LG recommends cleaning the filter every two weeks during heavy use. Remove it, rinse under warm water, let it dry fully, and replace it. If you haven’t cleaned the filter in months, this alone often restores full cooling performance.
Check that the unit is correctly sized for the room.
An AC unit that’s too small for its room will run constantly and still fail to reach the set temperature, which looks like a cooling problem but isn’t. LG AC cooling performance is generally good with effective temperature drops of 15 to 20°F in properly sized rooms. The Dual Inverter technology maintains more consistent temperatures with less cycling than traditional units. However, some users report cooling inconsistency issues where units cycle between cold and warm air every few minutes. If this cycling is consistent regardless of filter cleanliness, the unit may simply be undersized for the space.
Check whether the coils are frozen.
Ice forming on the evaporator coil is a specific and very common cause of sudden cooling loss. If you can see frost or ice through the front grille, turn the AC off and switch it to fan-only mode for an hour to let the ice melt. Then check the filter, since a dirty filter restricts airflow and is the most common trigger for coil freezing. Also check that no furniture or curtains are blocking the unit’s airflow. Once defrosted, the unit typically returns to normal cooling.
Check for refrigerant issues.
If the filter is clean, the coils aren’t frozen, and the unit is properly sized but still not cooling adequately, low refrigerant is the next possibility. Refrigerant doesn’t deplete in a healthy system, so low refrigerant means there’s a leak somewhere. This is not a DIY repair. A qualified HVAC technician must find the leak, fix it, and recharge the system. Adding refrigerant without fixing the underlying leak is a temporary fix that will recur. A technician will check refrigerant levels and recharge if needed, as well as inspect and repair any compressor-related issues and clean condenser coils to ensure proper heat exchange.
Check the condenser coils (split units and window units).
The outdoor unit or the condenser section at the back of a window AC needs to dissipate heat effectively. If the condenser coils are coated in dirt, grass clippings, or debris, they can’t release heat and cooling performance drops noticeably. Gently rinsing the outdoor condenser with a hose (with the unit powered off) often makes a meaningful difference.
Problem 2: LG Air Conditioner Not Turning On
If the unit is completely unresponsive, no display, no fan, nothing:
Check the power supply first. Confirm the outlet is live by plugging in something else. Check that the circuit breaker for the AC hasn’t tripped. LG window units in particular draw significant current on startup and can trip a breaker if sharing a circuit with other high-draw appliances.
Check the remote control. Replace the remote batteries before assuming the unit itself has failed. On LG split systems, the remote is required for most functions, and a dead remote looks exactly like a dead indoor unit.
Check that the unit hasn’t been accidentally locked. LG’s ThinQ-enabled units and some older models have a control lock feature that disables all physical buttons. Check your remote or panel for a lock indicator.
Perform a full power reset. Turn the unit off at the remote, then switch off the circuit breaker or unplug the unit entirely. Wait five full minutes before restoring power. This clears any error state the control board may have entered after a power surge or outage.
Check for timer settings. LG ACs have programmable on and off timers, and an accidentally set timer that’s in the off window will prevent the unit from starting even though everything else looks fine.
Problem 3: LG Air Conditioner Leaking Water
Water leaks are one of the three most widely reported issues with LG air conditioners. Water leaking from an AC isn’t unusual as a general concept, since cooling air naturally produces condensation, but it should be draining outside or collecting internally in the drain pan, not dripping into your room.
Window units: check the tilt angle.
LG window air conditioners are designed to be installed with a very slight backward tilt, typically about half an inch lower at the rear, so condensation drains outward. If the unit is level or tilted forward, water collects and eventually drips inside. Adjusting the angle is the fix.
Window units: P2 or FL error code.
The P2 or FL error code indicates that the drain pan in the unit is full. Under normal operating conditions, the drain pan will not need to be emptied. The unit is designed with a slinger fan that picks up water and slings it onto the condenser coil to help discharge heat. If the P2 or FL error appears, remove the unit from the window and drain it completely, then check that the slinger fan is spinning freely.
Split systems: blocked drain line.
Split AC indoor units drain condensate through a drain pipe to the outside. If this drain line gets blocked by algae, mold, or debris, water backs up inside the unit and drips from the indoor head. Flushing the drain line with a cup of water and a small amount of diluted bleach through the access point on the indoor unit clears most blockages. If water is actively spilling from the unit, turn it off until the drain is cleared.
Split systems: dirty evaporator coil.
A coated evaporator coil sheds water unevenly as it cools, causing drips instead of properly channeling condensate into the drain pan. This is resolved by cleaning the indoor coil, which is typically part of a professional servicing if you’re not comfortable doing it yourself.
Problem 4: LG Air Conditioner Making Unusual Noise
Noisy operation is among the most commonly reported LG AC problems. Understanding which type of noise you’re hearing points directly to the cause.
Rattling: Almost always a loose component, either something inside the unit has worked itself loose (a screw, a plastic panel clip, the filter frame), or debris such as a leaf or small object has entered the unit. Turn the unit off and check the filter and intake for anything that shouldn’t be there. Tighten any accessible panels.
Buzzing or humming: A continuous electrical buzzing usually points to a relay, capacitor, or compressor issue. A soft hum is normal compressor operation. A loud, irregular buzz or a buzz that changes pitch during operation warrants a technician inspection.
Clicking on startup or shutdown: Normal. Thermal expansion and contraction of plastic panels as temperature changes causes occasional clicks. If clicking is continuous during operation, it may indicate the compressor is struggling to start, similar to the start relay issue on LG refrigerators.
Gurgling: Water in the drain line is normal. Persistent gurgling combined with reduced cooling suggests the drain line is partially blocked.
Grinding or squealing: This is the most concerning category. A grinding or squealing sound from a split system’s outdoor unit or from a window unit’s fan section typically indicates a failing fan motor bearing. This will worsen over time and eventually the motor will fail completely. A technician should inspect it promptly rather than waiting until it stops entirely.
Problem 5: LG Air Conditioner Remote Control Not Working
Before assuming the remote has failed:
- Replace the batteries. This resolves the majority of remote issues.
- Make sure nothing is blocking the line of sight between the remote and the infrared receiver on the unit. LG AC receivers are usually located behind the front grille.
- Clean the infrared emitter on the front of the remote with a dry cloth. A dirty emitter reduces range significantly.
- If the unit responds to direct button presses but not the remote, the remote itself has failed. LG replacement remotes are widely available and inexpensive. Some LG smart air conditioners also allow control through the LG ThinQ mobile app, which bypasses the remote entirely on ThinQ-compatible models.
Problem 6: LG Air Conditioner Smells Bad
A musty, damp smell is the most common odor complaint and almost always means mold or mildew has grown on the evaporator coil or inside the unit. This happens when the unit isn’t run regularly, when it’s used frequently in high humidity, or when moisture collects and isn’t drying out properly between cycles.
Clean the filter immediately. Then run the unit in fan-only mode for 30 to 60 minutes after each cooling session to dry out the coil and internal surfaces. For persistent mold, a coil cleaning spray designed for AC units (available from hardware stores) applied to the evaporator coil and left to drain typically resolves the smell within a few uses.
A burning smell on first use after a long off-season is usually dust burning off the heating elements or coil and is normal for the first 20 to 30 minutes. If a burning smell persists beyond that, turn the unit off and have it inspected.
Problem 7: LG Air Conditioner Compressor Problems
Compressor failures affect approximately 8% of LG AC units after 2 to 4 years of operation. Consumer reviews from 2025 and 2026 include a case where a compressor stopped working after just 30 days on a newly purchased 25,000 BTU LG window unit.
Signs the compressor has failed: the fan runs normally, air blows through the unit, but no cooling happens at all. You may also hear a clicking sound as the compressor attempts and fails to start.
LG covers compressors under their standard warranty, and the Dual Inverter compressor used in LG’s split systems carries a 10-year warranty. If your unit is within the warranty period, contact LG before arranging any third-party repair. Compressor replacement outside of warranty runs $300 to $600 for most residential units.
LG Air Conditioner Error Codes: Complete Guide
Most LG split AC models display error codes directly on the LED display. LG smart air conditioners also allow error detection through the LG ThinQ mobile app. Always write down the exact error code before restarting the AC system.
For LED models without a digital display, the error code is shown through a blinking sequence: CH then the code digits repeat. For example, 5 steady blinks on the first LED means error code CH05. Recording the blink pattern on your phone makes it much easier to count accurately.
The most common LG AC error codes:
CH01 — Indoor room temperature sensor fault. The sensor monitoring room temperature has malfunctioned. Reset the unit first. If the code returns, the sensor needs replacing. Moderate DIY repair.
CH02 — Indoor pipe temperature sensor fault. The thermistor monitoring the evaporator coil pipe temperature has failed. Same approach: reset first, replace if code returns.
CH04 / FL / P2 — Condensate (water) formed inside the indoor unit is not being drained. Unplug or switch off the circuit breaker, wait 5 minutes, then restore power. If the error persists on non-humid days, product inspection is required. On high-humidity days this can trigger normally and is not necessarily a fault.
CH05 / E0 / CH53 — Communication error between the indoor and outdoor units. Try a full power cycle first. If it persists, the cause is often an unstable power supply, damaged wiring between the units, or a faulty control board. A technician is required for anything beyond the power cycle.
CH06 — Indoor fan motor speed abnormal. Clean the air filters first and check for any airflow blockage. If the error persists after filter cleaning, the fan motor itself has failed.
CH10 — Compressor temperature thermistor fault. The sensor monitoring compressor temperature has malfunctioned. Requires a technician to diagnose whether it’s the sensor itself or an actual compressor overheating issue.
CH21 — Inverter module overcurrent protection. The inverter module controlling the compressor has detected excess current, usually indicating a failing compressor or a fault in the inverter circuit board. Requires a technician.
CH38 — Refrigerant shortage detected. The system has sensed low refrigerant pressure, indicating either a leak or a measurement fault. A technician must check for a leak, repair it if found, and recharge the system. Do not ignore this code, running the compressor without adequate refrigerant damages it rapidly.
CH30 — Voltage going to the unit is too low for proper operation. This is not a defect but an indicator of improper voltage from the outlet. A certified electrician is required. If the error reappears after the voltage is corrected, the unit requires service.
First step for any error code: A full power reset (unplug or switch off the breaker for 5 full minutes) clears temporary faults and is always worth trying before concluding that a repair is needed. If the code clears and doesn’t return, it was a transient fault, not a hardware failure. If it returns consistently, the component named by the code needs professional diagnosis.
LG Air Conditioner Maintenance Checklist
Most LG AC problems are either preventable or made significantly worse by skipping basic maintenance. These are the things that actually matter:
Every 2 weeks during heavy use: Clean the air filter. This single task prevents coil freezing, poor cooling, increased energy consumption, and bad odors, all at once.
Once per season: Clean the outdoor condenser unit (split systems) or the back condenser section of a window unit by rinsing gently with a hose while the unit is off. Check the drain line is clear.
Once per year: Have the evaporator coil cleaned if you notice reduced cooling or persistent smells despite filter cleaning. Check the drain pan and drain line for buildup. On split systems, have a technician check refrigerant levels if it’s been more than 3 years.
At the end of the season: Run the unit in fan-only mode for 30 to 60 minutes before shutting it down for the winter to dry internal surfaces. Clean the filter before storage.
When to Call a Technician vs Fix It Yourself
DIY-appropriate:
- Cleaning or replacing the air filter
- Defrosting a frozen coil (turn off, fan-only mode for an hour)
- Adjusting window unit tilt angle for water leaks
- Flushing the drain line
- Replacing remote batteries
- Power cycling for error codes
Requires a technician:
- Refrigerant recharge (illegal to handle without certification in most countries)
- Compressor failure or replacement
- CH05 communication errors that persist after power cycling
- CH21 and CH38 error codes
- Grinding fan motor
- Any electrical burning smell beyond first startup
If your unit is within warranty, always contact LG first before arranging third-party service, as using an unauthorized technician can void the remaining warranty. LG’s warranty covers 1 year parts and labor on most units, and 5 to 10 years specifically on the compressor depending on the model.
If you’re considering replacing an aging LG AC unit or comparing LG with another brand, [LINK: our LG refrigerator problems guide] covers the broader reliability picture of LG appliances, and [LINK: our Samsung vs LG comparison] gives a category-by-category breakdown if you’re weighing both brands.