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Frost buildup [air conditioner] — LG Help Guide: Causes, Checks &

During Heating Mode, ice/frost builds up on the outside unit coils when the temperature outside the home lowers. During defrosting operation, as ice buildup melts to the ground, vapor (mist) is generated, and it might look like smoke. This is due to the melting of ice/frost buildup and is not a problematic issue or concern with the air conditioner.

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TroubleshootingAir Conditioners

What to Check First

  1. During heating, moisture in the air adheres to the surface of the evaporator in the outdoor unit that has become cold, causing frost. To prevent degradation of the heating performance due to frosts on the indoor unit, defrosting operation will start.
  2. During the defrosting operation, as the frost is melted vapor is generated and it might look like smoke. This is due to melting of frost and it is not a problem with the air conditioner.
  3. During Heating Mode, ice/frost builds up on the outside unit coils when the temperature outside the home lowers. During defrosting operation, as ice buildup melts to the ground, vapor (mist) is generated, and it might look like smoke. This is due to the melting of ice/frost buildup and is not a problematic issue or concern with the air conditioner.
  4. This guide was created for all LG single/multi-split air conditioner product models. Images or content presented herein may differ from your product.

Why This Can Happen

Symptoms can have more than one cause, and the correct steps depend on the exact model, installation and operating conditions. Use the checks above to narrow the issue before service.

Safety and Model-Specific Guidance

Stop troubleshooting if you notice burning, electrical damage, unsafe heat, gas odor, refrigerant concerns, or water near electrical components. Follow the official LG USA instructions for your exact model.

Frequently Asked Questions

What should I check first for Frost buildup [air conditioner]?

During heating, moisture in the air adheres to the surface of the evaporator in the outdoor unit that has become cold, causing frost. To prevent degradation of the heating performance due to frosts on the indoor unit, defrosting operation will start.

When should I stop troubleshooting and contact LG?

Stop if the product shows signs of electrical damage, burning, leaking near electrical components, or if the recommended checks do not resolve the issue. Use LG USA support for model-specific service guidance.

Does this guidance apply to every LG model?

Not always. Controls, error codes and service steps can differ by model. Confirm the exact model number and follow the linked LG USA article for model-specific instructions.

Related LG Products

These model pages are linked because the stored category or exact model matches this Help Library topic.

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Read the Official LG Guide