Airflow is one of the most important aspects of any heat and air conditioning system. Ironically, it is one of the most overlooked aspects and a root cause of many problems as well. The most common problems I see are airflow restrictions. This has some major consequences because it affects virtually every component of the system. For example, mechanical components such as the blower motor (i.e. indoor fan), the compressor (i.e. refrigerant pump), and the outdoor fan motor must all work harder to compensate for the lack of airflow. This excess work increases amperage and can cause electrical components to fail as well. As you can probably tell, this puts a lot of strain on the system and often leads to major component failures. Airflow restrictions can be caused by many factors; however, the most common is the simplest to resolve - replace your filters!
One very important point to consider with regards to filters is that they are NOT for air quality. This is a very common misconception. After all, it is easy to assume because of how manufacturers label their filter products. Over the counter filters promising to improve air quality often do so at the expense of your HVAC system because they actually restrict airflow. If you are concerned about air quality, the best thing you can do is to install indoor air quality equipment specifically designed to be installed on your system. Standard air filters are only there to protect your heating and air conditioning system, so adequate airflow must occur. If the filter becomes clogged with debris or pet hair the air coming back into the blower motor, heat exchanger, or coil is reduced. If you’re running your system in cooling mode, this reduction of airflow creates a pressure and temperature drop which can cause your indoor coil to freeze. As a side note, this same thing happens when the blower motor fails which is also an airflow restriction.