Weird Smell When AC Turns On: Causes and Solutions

You anticipate a pleasant wind and crisp air when you turn on your air conditioner. However, if you smell something odd, it can indicate that something is wrong. The common sources of strange odors, when the air conditioner is on, will be covered in this article, along with solutions.

Causes of Weird Smell When AC Turns On

  1. Mold and mildew buildup: Mold and mildew can grow in the damp and dark areas of your air conditioner, such as the evaporator coils and drip pans. When the AC turns on, it blows the spores into the air, causing a musty smell.
  2. Dirty air filters: If you haven’t changed your air filters for a while, they can become clogged with dust, debris, and even bacteria. When you turn on your AC, the air blows through the dirty filters, causing a stale or dusty smell.
  3. Electrical problems: If you smell a burning or metallic odor when your AC turns on, it can be a sign of an electrical problem, such as a malfunctioning capacitor or motor.
  4. Gas leaks: If you smell a rotten egg or sulfur-like odor, it can be a sign of a gas leak in your AC unit, which is a serious health hazard.
weird smell when ac turns on

Solutions to Weird Smell When AC Turns On

  1. Clean your air filters: One of the easiest ways to eliminate weird smells from your AC unit is to clean or replace the air filters regularly. This will improve the airflow and prevent bacteria and mold from building up in the filters.
  2. Clean the evaporator coils and drip pans: To get rid of musty or moldy smells, you need to clean the evaporator coils and drip pans with a mixture of water and vinegar. This will kill the bacteria and mold spores and prevent them from growing back.
  3. Call a professional technician: If you suspect an electrical problem or gas leak in your AC unit, it’s important to call a professional technician to assess and repair the problem. Do not try to fix it yourself, as it can be dangerous.
  4. Use an air purifier: An air purifier can help eliminate any odors and pollutants in the air, ensuring that your AC unit blows clean and fresh air.
  5. Schedule regular maintenance: Regular maintenance of your AC unit can prevent weird smells and identify any potential problems before they become a bigger issue. Have your AC unit serviced by a professional technician at least once a year.

Preventing Weird Smell When AC Turns On

Here are some preventive measures to avoid weird smells from your AC unit:

  1. Change air filters regularly: Change your air filters every three months or as recommended by the manufacturer to prevent buildup of bacteria and mold.
  2. Use a dehumidifier: A dehumidifier can help reduce the moisture in the air, preventing mold and mildew from growing in your AC unit.
  3. Clean the condensate drain line: The condensate drain line can become clogged with debris and bacteria, causing a musty smell. Clean it regularly to prevent buildup.
  4. Use natural remedies: Natural remedies such as baking soda or essential oils can help absorb any odors in the air.


Odd smells coming from your air conditioner when it is turned on could indicate a number of issues, including gas leaks, mold and mildew buildup, unclean air filters, and electrical issues. You can use an air purifier, hire a professional technician for repairs, clean your air filters and evaporator coils, schedule routine AC maintenance, and use an air purifier to remedy the issue.

Change air filters frequently, use a dehumidifier, and clean the condensate drain line to stop strange odors from developing.