Genuine Fujitsu 9366378020 Outdoor Propeller Fan (3-Blade) is the three-blade fan that mounts on the outdoor unit's fan motor behind the protective net, drawing air through the outdoor coil. Moving that air across the coil is the fan's whole job, so a cracked, chipped or unbalanced blade set leaves the outdoor unit turning a fan that no longer moves the air it should, and running rougher while it does. A sound blade set keeps the outdoor unit quiet and steady.