The work of an AC filter is to filter the air entering the car. It does this work by removing all the pollutants and debris. That is why it is also known as a cabin air filter. If you feel the presence of an unpleasant odor in your car, it can be because of a malfunctioning AC filter. More so, if the unpleasant odor persists when you turn on the AC in your automobile, it is for sure because of choked AC Filters. Other indicators can be weak airflow even at the maximum setting, a whistling sound, or excessive noise.
Many AC filters come with mileage stamps; detailing the required change of air filters after specified mileage. If you don’t have those mileage stamps, it is advisable to change the air filters after about 25,000 - 30,000 kilometers.