The filter comes first
A clogged filter sits behind a surprising share of heating and cooling complaints. It chokes the airflow, the system runs longer to reach the thermostat setting, and on the cooling side the indoor coil can freeze. Filters are cheap, and changing one takes a minute once you know the size, which is printed on the edge of the one already in the system.
What a tune-up is for
A yearly check is less about cleaning and more about catching the small problem before it turns into a no-heat night. On the heating side that means the burners, the flame sensor, the safety controls and the venting, plus a carbon monoxide check. On the cooling side it means the coils, the refrigerant charge, the condensate drain and the electrical parts that wear. Keep a record of each visit. The same repair coming back year after year says something about the system’s age.
A rhythm for New Jersey
Schedule the heating check for early fall, before the first cold snap brings every furnace in the neighborhood on at once, and the cooling check for spring. Between visits, keep the outdoor unit clear of leaves and snow, and watch the condensate drain line in summer. For what the air itself needs, see indoor air quality.