When I turn my AC on 1,2 and 3 it's fine but on the 4th setting my blower motor makes a deep hum. Yesterday I put my hand on it so I know it's coming from there. My question is, could it be the $24 BM resistor or should I drop the 3 screws and the BM on the inside passenger side to see if something me be throwing it off balance ? Anyone else have this little annoying problem ?

 

If your fan blows on 1,2,3 your resistor is fine.

Remove the blower motor and look for obstructions on the wheel, or a bearing could be worn in your motor.

 

Ok thanks