I read many years ago that over 50% of all air conditioning breakdowns were due in one way or another to lack of interior airflow. Dirty filter, clogged coil, tight blower motor, slipping drive belt, kinked flex duct, etc. So my loudest advice to everybody I met was change the filter and get the system serviced regularly. Yet the vast majority of my calls were air flow related.
People tend to forget about the AC so long as it works, and so often the filter gets ignored. They don't realize restricted airflow leads to evap coil freeze-ups, and liquid refrigerant migration back to the outside condensing unit, where it destroys the compressor. So a stupid $7 filter can cost a homeowner a $2000 compressor of $12,000 system!
