DIAGNOSIS The primary air filter is not immediately obvious. It's a large, flat filter behind the front grille.
FIX Power off the unit. Press the two tabs on the top of the front panel, near the display. Pull the top of the panel forward, then lift it off. The large gray mesh filter is right there. Slide it out. Wash with lukewarm water and let dry completely.
IF THAT DIDN'T WORK If the panel won't release, you're not pressing the hidden tabs correctly. Look for two small indentations on the top edge of the bezel. Press in firmly there.
HEADS UP Never run the unit without the filter. It will clog the evaporator coil with dust in days, killing cooling performance and potentially the unit.