Why does ac smell after turn off?

The smell from an air conditioning (AC) unit after it is turned off can be attributed to a buildup of moisture and dust within the system. When the AC runs, it cools the air and can create condensation, which may lead to mold or mildew growth on the evaporator coils or in the drainage pan. Additionally, dust and debris can accumulate, leading to unpleasant odors when the system is no longer circulating air. Regular maintenance and cleaning can help mitigate these smells.