One of the most obvious signs that a cabin air filter needs to be replaced is reduced airflow in the ventilation grilles. When clogged with dirt, the resulting restriction reduces the amount of air reaching the cabin, meaning you may need to turn up the air conditioner higher than usual. This places a burden on the air conditioning system as it tries to blow more air into the cabin, resulting in an increase in fan noise and an inability to maintain a constant cabin air temperature. Not only can a clogged cabin filter reduce the volume of air that can pass through, but it can also create a stench of dust and moisture when the HVAC system is turned on.
In extreme cases, the clogged filter can completely obstruct the airflow, either by causing the fan motor to fail or by sucking the filter out of the housing along with all the debris that leaks out. The cabin air filter prevents dust, pollen and other debris from entering the passenger compartment through the climate control system. It is made of multifiber cotton sheets or manufactured fabric and traps dirt, pollen, dust, smoke, bacteria, spores, allergens and exhaust gases before they can enter the interior of your car. It is important to ensure that the cabin air filter is working properly and changed regularly, especially if driving in dusty or heavily polluted conditions.
Most vehicles place the cabin air filter behind the glove box door, while some place it under the hood or elsewhere. Changing the cabin air filter regularly will ensure that passengers don't have to roll down the windows to get some fresh air and that your car's air conditioning system is able to maintain a comfortable temperature. Failing to do so can lead to a variety of problems, from reduced airflow and increased fan noise to complete obstruction of airflow and an unpleasant smell.