The manufacturer recommends replacing the cabin air filter at the specified intervals to maintain the performance of the HVAC system. For Legacy models from 2004 and earlier, remove the glovebox, disconnect the resistor connector, remove the clips and pry the cabin air filter cover from the cooling unit. The cabin air filter cover is positioned vertically. Remove cabin air filler A (lower cabin air filter), noting that the installation arrow mark faces up. Then, remove cabin air filter B (upper cabin air filter). For 2005 and later models, remove the instrument panel side cover, remove the clip and the damper string and lower the glovebox door, and remove the cabin air filler, noting that the arrow on the face of the cabin air filler faces up. For Forester models from 2002 and earlier, working below the glovebox, remove the two clips using a flat-bladed screwdriver to unlock the hinge, remove the cabin air filter cover from the cooling unit, remove cabin air filter A (front cabin air filler), noting that the installation arrow mark faces up, and remove cabin air filter B (rear cabin air filler). For 2003 and later models, remove the glovebox and glovebox panel, remove the cabin air filter cover, and remove the cabin air filter, noting that the arrow on the face of the cabin air filter faces up. For all models, install a new cabin air filter with the arrow facing up. Installation is the reverse of removal.