Locate and Open Air Filter Cabinet
When it’s time to inspect your filter, always be sure to turn off power to the system. You can do this either at the thermostat, the breaker box, or using the shutoff switch located on/near the indoor unit (often looks like a light switch).
The exact location of the filter can vary depending on the indoor HVAC unit and type of system. Most single-home residential systems include either a vertical or horizontal indoor air handler unit (furnace or fan coil), typically in a basement, furnace/utility closet, garage or sometimes an attic. Look for a filter cabinet along the sides, top or bottom of the blower cabinet. The filter may be positioned horizontally or vertically, depending on the orientation of the air handler in the indoor unit. In some cases, especially on older models, the filter may be found inside the blower cabinet. If you live in a multifamily apartment or condo unit, the filter may be located in an in-wall return air grill.
Once you have ensured that power is shut off and located the filter, take a moment to determine the direction air flows through the system. Some filters will include air flow arrows to ensure proper installation. If arrows are present, take note of the direction they are pointing so you can properly re-install the old one or install the new one. Now, remove the filter from its housing and inspect it for excessive build-up of dust, dirt and debris.
Decision Time: Clean or Replace
Sometimes when you pull out the filter, it’s painfully obvious whether it’s time to clean or replace: if caked on dirt and dust are falling off the surface, it’s probably restricting air flow and you’ll want to take action. If it’s only lightly covered, or you can still see light through the filter material, you may want to clean the filter and then check again in another month. If it’s somewhere in between, you can default to the filter manufacturer’s recommendations or use your own judgment based on your own experience.
If you are replacing or changing air conditioner filters, be sure to either measure the old filter or take note of its dimensions if printed on the casing before you throw the old one away. You will need these dimensions to purchase a replacement if you don’t have a replacement filter at home already.
If you are cleaning the filter, be sure to follow the manufacturer’s recommendations. Many filters, whether disposable or re-usable can be cleaned with a vacuum cleaner nozzle attachment, being careful not to tear the filter material.
Insert the Clean Filter and Turn the AC Unit On
Carefully slide the new or cleaned filter back into its housing with the airflow arrows pointing in the correct direction. Properly secure the cabinet or panel cover, then restore power to the system and turn it on.