DIAGNOSIS A foreign object is caught in the fan blower wheel or the plastic plasma wave housing is loose.
FIX Unplug the unit. Remove the rear carbon filter and the front True HEPA filter. Look into the cavity for the fan blower wheel. Use a flashlight and tweezers to remove any debris like plastic wrap or large dust clumps. Also check the two plastic plasma wave housings on the sides—press them firmly to ensure they're snapped into place.
IF THAT DIDN'T WORK The blower wheel shaft may be out of balance or the motor bearings are failing. This requires disassembly and part replacement. Contact Winix support.
HEADS UP Always unplug before reaching inside. Do not attempt to lubricate the motor. It is a sealed unit.