This is true of all heaters, regardless of price. If the heater was banged around at all on shipping some important part clearances, like the tiny space between the spinning fan and the heater case, might have have changed since it was tested in China. So..before starting the unit, remove the cap on the air inlet fan, and make sure it spins freely with no noise. Use your finger to spin it. If you hear plastic on plastic rubbing, a noise like a spinning plastic fan hitting the plastic housing, you must fix the fan clearance problem, sand paper, shims, adjust fan on shaft, flex the plastic away a few times quickly until it warms and stays, or even use a hair dryer. Just make sure the fan spins silently before turning on.
Garry Abram Fisher 
