DIAGNOSIS Routine maintenance required. Focus on two user-serviceable parts: the air filter and the exhaust hose interior.
FIX For the filter: Power off the unit. Open the front panel, remove the foam filter. Wash it gently in lukewarm water with mild detergent. Rinse and air-dry completely before reinstalling. For the hose: Disconnect from unit and window bracket. Use a vacuum cleaner hose attachment to remove dust from inside. Wipe the exterior with a damp cloth.
IF THAT DIDN'T WORK If there is a persistent musty smell, mold may be present. After cleaning the filter, run the unit on Fan mode only for 2-3 hours in a dry room to evaporate moisture from the internal coils.
HEADS UP Never use harsh chemicals, abrasives, or high-pressure water on any part of the unit. Do not attempt to clean the internal evaporator or condenser coils.