How to Fix LG Air Conditioner Error F4

What error F4 means

Error F4 on an LG air conditioner means the unit is low on refrigerant (gas). LG's own Guide to Error Codes lists it with CH38: CH38 / F4 errors indicate that the air conditioner is low on refrigerant, and the warning is designed to protect the appliance from potential damage. LG's troubleshooting article for the same group says that CH32, CH33, CH36, CH38 or F4 point to low refrigerant levels, or more broadly to a refrigerant or compressor-related problem, which may result from a temporary power issue, or a malfunction in the outdoor unit's compressor, drive, protection circuit, or internal electronic components. The guide also notes that the test-run codes CH90 / CH91, which are displayed during the test run phase to prevent damage to the appliance, may on some models be displayed as F4. LG's advice depends on timing: if F4 appeared after installing or relocating the AC, the error likely points to a refrigerant shortage and the installation technician should inspect the unit and the piping connection; if it appeared during normal use, the cause may be temporary and electrical, and a 5-minute power cycle comes first.

Why error F4 happens on a LG Air Conditioner

On a LG Air Conditioner, error F4typically resolves to one of three root-cause categories. They’re ordered cheapest-to-verify first — start at the top and only escalate if the first cause is ruled out.

• Mechanical: blockage, obstruction, or worn moving part. A common cause across LG Air Conditioners in India — air filters clog and fan bearings and drain lines collect dust and sludge. Our step-by-step fix below targets this category first because it’s the cheapest to verify and resolvereports.
• Electrical: voltage spike, sensor fault, or PCB anomaly. India’s grid carries more voltage fluctuation than many appliance design tolerances assume, and a routine surge or sag can be enough to throw F4. If you’ve had recent voltage events (lights flickering, AC tripping), start your investigation here. A working stabilizer prevents this entire category.
• Software / configuration: stuck child-lock, demo-mode, or pending firmware reset.Less common but the cheapest fix when it applies — a 60-second factory reset clears it. We list this last because it’s rarely the actual cause, but check it before disassembling anything.

Safety first

Step-by-step fix

1. 1

   Step 1

   Note when F4 first appeared

   LG's guidance hinges on timing. If F4 showed up within days of installation, or after the AC was shifted to another room or house, LG says the error likely points to a refrigerant shortage and that the piping connection may need checking by the installation technician. If the AC has run normally for months, LG says the issue may be temporary, caused by unstable power or other electrical factors, so reset first.

   Pro tip: Photograph the display showing F4 and the model label on the indoor unit.

2. 2

   Step 2

   Perform the 5-minute power cycle

   Switch the AC off with the remote. Unplug the power cord or turn off the circuit breaker, wait for 5 minutes, then restore power and start the AC in Cool mode. This is the reset LG specifies for F4 that appears during use.

   Caution: Reset once. If F4 returns, repeated restarts add no refrigerant and only run the compressor on a low charge.

3. 3

   Step 3

   Check the cooling over the next hour

   If F4 cleared, run the AC and watch for the signs of a low gas charge: weak cooling, warm air at the indoor unit, or frost on the thin copper pipe at the outdoor unit. Steady, normal cooling with no repeat means the trip was electrical. Weak cooling means the code is likely to return and the charge needs checking.

   Pro tip: Use a moderate set temperature such as 26 °C for the test run.

4. 4

   Step 4

   Look at the outdoor pipe joints without touching them

   With the circuit breaker off, look at the two copper pipes where they enter the outdoor unit and at the flare nuts on the service valves. Oily, dark staining on the insulation or around a nut is the typical sign of a slow leak at a joint. This is information for the technician; do not loosen any nut or cap.

   Caution: Never try to add refrigerant yourself. The circuit is pressurised and must be charged by weight with proper equipment.

5. 5

   Step 5

   Call the installer if the unit is new or was moved

   For a recently installed or relocated AC, LG says to contact the installation technician; their details are usually on the business card left at installation or on a sticker on the side of the unit. A short charge, or a flare joint that was not made properly during the move, is the installer's responsibility. If F4 appeared during the installer's test run, LG notes that CH90 / CH91 test-run errors can be displayed as F4 on some models, so the installer should complete and verify the test run.

   Pro tip: Ask for a pressure test of the piping, not just a top-up; topping up a leaking system only delays the next F4.

6. 6

   Step 6

   Request LG service if F4 returns during normal use

   If the reset did not hold and the AC is not newly installed, LG's instruction is to contact LG support for assistance. Call LG customer care with the model number and the code F4. The technician will check the refrigerant charge, locate any leak and repair it before recharging. For a unit in warranty, use LG authorised service only so the compressor warranty stays intact.

   Caution: Running an AC that keeps tripping F4 risks the compressor, the costliest part of the system.

Fixed it? Protect it next time. See an extended warranty plan for your Air Conditioner →

Common mistakes LG Air Conditioner owners make with error F4

These six anti-patterns turn a routine 30-minute fix into a costly repair or warranty void. Read before starting.

• Forcing a stuck door, lid, or panel. Prising open a LG Air Conditioner housing while it is in a fault state. Forcing it usually breaks the latch or sensor — turning a small part replacement into a full service call. If the door won’t open, run the safety-disconnect step first, then try again.
• Repeated unplug-and-replug as a “reset” ritual. Cycling power three or four times without diagnosing the underlying cause stresses the PCB and can convert a soft fault into a permanent firmware-corruption code. Reset once, observe whether the error returns immediately, then move to actual diagnosis if it does.
• Pouring water (or any liquid) into electronics-adjacent areas to flush a blockage.Even a small amount near the PCB or main wiring harness can cause permanent damage that voids warranty. The unit’s drainage paths exist for a reason; if a blockage isn’t cleared by the manual procedure, it isn’t getting cleared by improvisation either.
• Skipping the safety-disconnect step.“I’ll just check quickly” is the most expensive sentence in appliance repair. Working live on a 230V circuit (especially with a hot or wet appliance) carries real shock risk and instantly voids any warranty claim. Disconnect, wait two minutes for capacitor drain, then proceed.
• Buying counterfeit replacement parts on Amazon.in. Red flags: price below 60% of LG authorised price, generic packaging without a model-compatibility list, seller name that doesn’t match a known LG parts distributor, listings dated within the last 30 days with no reviews. Counterfeit parts often work for 2-3 weeks then fail with a different error, costing you double.
• Calling an “independent” technician for a warranty-covered unit. Indian appliances under LG warranty must be serviced by authorised technicians or the warranty voids permanently. Even if the warranty is expired, third-party local technicians often replace working parts to inflate the bill — verify each part swap by asking to see the failure on the old part before they install the new one.

Preventing future F4 on your LG Air Conditioner

The fix above resolves the current instance. These five maintenance habits prevent it from coming back, specific to LG Air Conditioners in Indian operating conditions (hard water, voltage variability, monsoon humidity).

• Monthly: wash the air filters and clear the drain line. Hard-water deposits and everyday debris are a frequent cause of recurring F4 in India, and a few minutes each month is the cheapest way to avoid a repeat.
• Quarterly: descale water-touching components. Use food-grade citric acid or a LG approved descaler for hard-water regions (Bangalore, Hyderabad, large parts of Maharashtra and Tamil Nadu). Skipping this in a hard-water zone shortens the life of the heating and water-touching parts.
• Run the unit through a working stabilizer. A mainline stabilizer sized for Air Conditioners is the cheapest protection against voltage-induced F4 occurrences. The MCB on your distribution board is not a substitute — it trips on overload, not on under-voltage or surge.
• Decide AMC vs DIY honestly. Compare the LGAMC quote against what you have actually spent on service. If your unit is >5 years old and you’ve had two service calls in the last 18 months, an AMC usually pays for itself. Younger units with no service history: DIY plus stabilizer is cheaper.
• Watch monthly for early-warning signs. Unusual noise during a specific cycle phase, water spotting, mild burning smell — any of these means a service call within a week, not a wait-and-see month. Catching F4-precursor symptoms early turns a major repair into a routine maintenance visit.

If error F4 returns within 30 days of completing the fix above, escalate directly to LGauthorised service — repeat patterns within a month indicate a deeper fault (worn bearing, failing PCB, leak that wasn’t fully identified) that surface-level repair won’t resolve. Document the dates and circumstances of each occurrence; the service centre will use this to prioritize root-cause investigation.