Step 5 · Check and Clean the Evaporator Coil (Indoor Unit)

This step can be more involved and may require removing an access panel on the indoor air handler. Locate the evaporator coil (often above the furnace or air handler fan). It is typically a finned metal component. Inspect it for any accumulation of dust, dirt, or mold. If it appears dirty, you can use a soft brush or a vacuum with a brush attachment to gently clean the fins. For heavier buildup, a no-rinse evaporator coil cleaner spray may be used, following the product's directions. Ensure the condensate drain pan and drain line are also clear of debris to prevent water backup.