Quick Answer

When an LG portable air conditioner runs but does not cool, the most common causes are a dirty air filter, a kinked exhaust hose, a tripped CH05 freeze-up code, or low refrigerant. Clean the air filter, straighten the exhaust hose, confirm the room is at least 65 F, and power cycle the unit for 60 seconds. If cooling does not return, the next suspects are the coil sensor, the control board, or a sealed-system refrigerant issue that needs a service technician.

Before You Start

A few setup and safety checks will save you time and protect the unit from a short or a false sensor reading:

  • Unplug the unit before removing the air filter, opening the drain port, or pressing any control panel button combinations.
  • Move the unit away from the wall so you can reach the back and the exhaust hose.
  • Confirm the room temperature is at least 65 F (18 C). A cold room prevents cooling even on a healthy unit.
  • Have a soft brush, a vacuum with a brush attachment, and a few dry towels nearby.
  • If the unit has been running for less than 30 minutes, give it time to cool down before opening anything.
  • If the unit is still under warranty, call LG support at 1-800-243-0000 before opening the sealed case.

Common Causes

CauseLikelihoodWhat to Check
Dirty or clogged air filterHighRemove the filter, rinse with warm water, let it dry fully
Blocked or kinked exhaust hoseHighStraighten the hose and confirm the window kit seal is tight
Room temperature too low for Cool modeHighConfirm the room is at least 65 F
Tripped CH05 freeze-up codeHighLet the coil thaw for 60 minutes with the grille open
Ice on the evaporator coilHighOpen the front grille and look for frost on the coil
Blocked condensate drain lineMediumCheck for standing water in the base pan and a slow drain
Coil temperature sensor faultMediumSensor reads very low even with a warm coil
Low refrigerant (rare)LowOily residue, hissing sound, never cools well

Step-by-Step Troubleshooting

Step 1: Confirm Cool Mode and Thermostat Setting

Before any physical checks, confirm the unit is actually in Cool mode and the thermostat is set below the room temperature.

  1. Press the Mode button on the control panel or remote until Cool is selected.
  2. Set the thermostat to at least 5 F below the current room temperature.
  3. Set the fan speed to High for the first 5 minutes.
  4. Wait 10 minutes and feel the air output. If the air is still warm, move on.

Step 2: Clean the Air Filter

A clogged filter is the single most common cause of an LG portable AC that runs but does not cool. Reduced airflow over the evaporator coil drops the coil temperature below freezing and the sensor trips CH05, pausing the compressor.

  1. Open the front grille and slide the air filter out.
  2. Rinse the filter under warm water. Do not use hot water.
  3. If the filter is heavily soiled, soak it for 10 minutes in warm water with a small amount of mild dish soap.
  4. Let the filter air dry completely.
  5. While the filter is out, vacuum the inside of the grille opening with a brush attachment.
  6. Refit the filter, close the grille, and run Cool mode for 30 minutes.

Step 3: Inspect the Exhaust Hose and the Window Kit

A restricted exhaust path traps hot air around the cabinet and starves the evaporator of return air. Both conditions can prevent cooling.

  1. Move the unit away from the wall and inspect the full hose run.
  2. Straighten any kinks in the hose. LG portable AC hoses are typically 5 inches (12 cm) in diameter.
  3. Confirm the hose is not crushed behind the cabinet or pinched by the window kit.
  4. Check the window kit seal. Hot air leaking back into the room raises the cabinet temperature.
  5. Confirm the hose length is within LG’s recommendation. Extra-long hose runs reduce cooling efficiency.
  6. Restart the unit in Cool mode.

Step 4: Power Cycle and Reset

If cleaning and inspection did not restore cooling, do a full power cycle.

  1. Turn the unit off using the control panel or remote.
  2. Unplug the power cord from the wall outlet. Wait at least 60 seconds.
  3. While unplugged, press and hold the power button for 10 seconds to drain residual charge.
  4. Plug the cord back in directly, not through an extension cord.
  5. Start in Cool mode and wait 10 minutes.

For a factory reset on most LG portable ACs, hold the Up arrow and Fan Speed buttons together for 5 seconds. The display should reset.

Step 5: Check for CH05 Freeze-Up Code

LG portable ACs use CH05 as the formal evaporator freeze-up code. If CH05 is showing, the compressor is paused to let the coil thaw.

  1. With the unit powered off and unplugged, open the front grille.
  2. Look at the evaporator coil. If you see frost or ice, leave the unit unplugged with the grille open for at least 60 minutes.
  3. Confirm the room is at least 65 F.
  4. Inspect the air filter and exhaust hose again. Even a lightly dirty filter can trigger CH05.
  5. Power cycle the unit and start in Cool mode.

Step 6: Test the Coil Temperature Sensor

If cooling still does not return after a clean filter, a clear hose, a power cycle, and a 60-minute thaw, the coil temperature sensor is the most likely culprit.

  1. With the unit unplugged, locate the coil sensor. It is usually clipped to the suction line of the evaporator coil.
  2. Inspect the wiring for a loose connector, corrosion, or a pinched wire.
  3. If you have a multimeter, compare the resistance of the coil sensor against the room temperature sensor. They should track within a few hundred ohms at the same ambient temperature.
  4. If the coil sensor reads as an open circuit or a wildly different value, replace the sensor.
  5. Reassemble and test.

Why an LG Portable AC Stops Cooling

A few patterns explain why an LG portable AC runs but does not cool:

  • The filter is dirty. Reduced airflow over the evaporator coil drops the coil temperature and trips the freeze-up code.
  • The exhaust hose is kinked. A slow exhaust traps heat in the cabinet and confuses the sensors.
  • The room is too cold. Below about 65 F, Cool mode cannot operate efficiently.
  • The coil is iced. A deep freeze takes an hour to thaw. Restarting Cool too soon re-triggers the sensor.
  • The drain pan is full. Standing water in the base pan chills the coil sensor directly.
  • The refrigerant is low. A leak in the sealed system is a service-level repair.

When to Call a Technician

Stop DIY work and contact LG support at 1-800-243-0000 or a qualified service technician if any of the following is true:

  • The unit still does not cool after a clean filter, a clear exhaust hose, a power cycle, and a 60-minute thaw.
  • You hear a hissing or bubbling sound anywhere in the cabinet, which can indicate a refrigerant leak.
  • The unit trips the breaker as soon as you restart it.
  • You see oily residue on the copper lines or around the evaporator coil.
  • The display shows additional error codes alongside CH05.
  • The unit is still under warranty. Opening the housing can void coverage.

If the unit is out of warranty and you have ruled out the filter, the hose, the room temperature, the drain, and the sensor, the most likely remaining cause is a sealed-system fault or a control board fault. Both are service-level repairs.

LG-Specific Notes

A few LG-specific quirks are worth knowing when troubleshooting a portable AC that is not cooling:

  • CH05 is the formal freeze-up code. E5 may also appear alongside it. Either code points to the same root cause.
  • CH04 is the formal full-tank code. LG portable ACs may show P1 instead of CH04 on some models. Both mean the tank is full.
  • Factory reset combination. Hold Up arrow and Fan Speed for 5 seconds. The display will reset.
  • Warranty support. LG USA supports portable ACs at 1-800-243-0000. Have the model number from the back of the unit ready.
  • Drain pump on some models. Higher-end LG portable ACs have an internal condensate pump. A failing pump can prevent cooling even when the tank is empty.