LG Window AC Not Cooling

Common Symptoms

• LG window AC running but room is not getting cooler
• Fan blows but compressor cycles off frequently (Energy Saver mode symptom)
• LG filter clean indicator light is illuminated
• Error code E1 or CH shown on LG display
• Weak airflow despite unit appearing to run normally
• Warm air coming from vents when set to Cool mode
• Unit powers on and off repeatedly

Most Likely Causes

1. 1

   Energy Saver Mode — Compressor Cycles Off Frequently

   LG window ACs have an Energy Saver mode that uses a built-in room thermostat to cycle the compressor (and sometimes the fan) on and off based on the room temperature relative to the set point. When the room reaches the set temperature, the compressor shuts off — the fan may continue at low speed or also shut off depending on the model. In a hot room with a leaky window seal, Energy Saver mode causes the room to warm again quickly, triggering another cooling cycle — but the unit still spends significant time with the compressor off. To maximize cooling in hot conditions, switch to COOL mode (not Energy Saver) so the compressor runs continuously.

2. 2

   Dirty Air Filter — LG Recommends Monthly Cleaning

   LG recommends cleaning the window AC air filter monthly during the cooling season. The filter is located behind the front grille and is accessible without tools on most LG models. A clogged filter severely restricts airflow over the evaporator coil, reducing cooling capacity and eventually causing the coil to ice over — leading to warm air discharge. Many LG models illuminate a 'FILTER' indicator light after a set number of operating hours as a reminder. This light does not mean the filter is necessarily dirty, but it should be used as a prompt to inspect and clean.

3. 3

   LG Error Code E1 — Room Temperature Sensor Fault

   Error code E1 on LG window AC units indicates a fault with the room temperature (thermistor) sensor. The room temp sensor is used to regulate compressor cycling and maintain the set temperature. A failed sensor causes the unit to behave erratically — running the compressor continuously or not at all. E1 is sometimes triggered by a loose sensor wire connector. Unplug the unit for 30 seconds and plug back in to attempt a reset. If E1 returns after reset, the temperature sensor likely needs replacement — this requires partial disassembly of the front panel; contact LG support or a certified technician.

4. 4

   LG Error Code CH — Communication Error

   Error code CH on LG air conditioners indicates a communication error between the main control board and another internal component (often the inverter board or a sensor board). The fix is to unplug the unit from the wall outlet, wait 30–60 seconds, and plug back in to allow the control boards to reinitialize. If CH persists after multiple power cycles, a control board or sensor component has failed and requires professional service.

5. 5

   Condenser Coil Fins Blocked — Heat Rejection Impaired

   The condenser coil on the back (outdoor-facing side) of the window AC must expel the heat removed from the room into the outdoor air. Bent condenser fins, cottonwood fluff, debris, or dirt packed into the fin array block airflow through the coil and prevent heat rejection. The refrigerant stays warm, cooling capacity drops, and the compressor may trip on a high-pressure overload. Inspect the rear of the unit for debris accumulation and clean with a vacuum and soft brush attachment — with the unit unplugged.

6. 6

   Window Seal Gaps — Hot Air Infiltration

   LG window AC units ship with foam or vinyl insulating panels that seal the gaps between the unit chassis and the window frame. Over time, these panels compress, shrink, or are not properly seated, allowing hot outdoor air to flow directly into the room alongside the unit. This 'infiltration' load can be significant on a hot day — the AC cools air it just conditioned from the outside, making the unit feel undersized. Inspect the seal around the entire unit perimeter and replace foam insulation tape or accordion panels as needed.

Quick DIY Checks

1. 1Check and switch out of Energy Saver mode: press the MODE button on the LG unit or remote to cycle through available modes. Confirm the unit is in COOL mode — not Energy Saver (sometimes labeled ES or shown with a leaf icon). In Cool mode the compressor runs continuously whenever the room temperature is above the set point. Set the temperature at least 4–5°F below the current room temperature. Listen for the compressor to engage (a slightly louder, vibrating sound from the unit) within 1–2 minutes. If the compressor was cycling off in Energy Saver mode, switching to Cool mode alone may resolve the inadequate cooling complaint.
2. 2Clean the air filter: open the front grille of the LG unit (most models have a grille that pulls forward or lifts up — check your owner's manual). Slide out the mesh air filter. Rinse under warm running water, brushing gently if needed, and shake out excess water. Allow the filter to air-dry fully (30–60 minutes) before reinserting. After reinserting, press and hold the FILTER RESET button (location varies by model — check the manual) to reset the filter reminder light. If the filter is torn or deformed, order a replacement (LG part number specific to your model, or a compatible aftermarket filter).
3. 3Perform a PTAC-style reset (unplug 30 seconds): unplug the LG window AC from the wall outlet. Wait a full 30 seconds — this allows the control boards and capacitors to fully discharge and reset. Plug back in. Wait 3 minutes (the compressor protection delay prevents the compressor from starting sooner). Set to COOL mode at a low temperature and confirm the compressor activates. This reset clears minor fault flags and reinitializes the sensor reading on many LG models — it resolves CH errors and some E1 false trips caused by power fluctuations.

1. 4Look up and address LG error codes on the display: if E1 appears, note it and attempt the unplug-30-second reset described above. If E1 returns after reset, the room temperature sensor has likely failed — partial front-panel disassembly is needed to inspect and test the sensor connector. If CH appears, unplug the unit, wait 60 seconds, and plug back in. Multiple CH codes after power cycling indicate a control board failure — contact LG support or schedule professional service. Other LG error codes: CB / F1 / F2 — refer to your model's owner's manual (available on lg.com/us/support) for specific descriptions.
2. 5Inspect and clean the condenser coils (outdoor-facing side): with the unit unplugged and removed from the window (or with access to the rear), use a vacuum with a soft brush attachment to remove debris from the rear condenser fin array. Inspect the fins for bending — a fin comb can straighten bent fins to restore airflow. Do not spray water into the unit from the room side. If accessible, a gentle rinse of the rear coil with a garden hose (unit unplugged, held away from electrical components) removes packed debris effectively. Allow to drain before reinstalling.
3. 6Inspect and reseal window installation gaps: with the unit installed, inspect the foam accordion panels on each side of the unit and the top rail seal. Press firmly on all foam seals and look for daylight or air movement around the perimeter. On a hot day you can feel the infiltrating warm air with your hand. Replace compressed or missing foam seals with window AC foam insulation tape (available at hardware stores). Ensure the accordion panels fully extend to the window frame on both sides with no visible gaps.

Repair vs Replace

Recommended Tools & Parts

• LG Window AC Replacement Air Filter

  OEM or compatible replacement mesh air filter for LG window AC units. Replace when the existing filter is torn, deformed, or permanently discolored. Match to your LG model number — filters are model-specific on LG units. Available on LG's parts website or through compatible aftermarket suppliers.

  $10–$25

  Buy on Amazon →

• Window AC Foam Insulation Tape

  Self-adhesive closed-cell foam tape for sealing gaps around window AC installations. Replaces compressed or missing accordion panel seals to prevent hot outdoor air infiltration. Available in various widths — measure your gap before purchasing.

  $8–$18

  Buy on Amazon →

Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.

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