at full and 2,3 below full on my 99 s80 blow makes an extremely loud noise like a rumbly humm.... uh hard to describe... can voise sms noice if anyone wants to hear it.. any idea on a fix for this blower blows fin heater works ac works just makes a loud deep rumble/humm noise.

 

Maybe something in there.
Maybe motor is bad.

 

Mine was making a loud noise also. I took it out and a few pieces of plastic fell out with it. I then proceeded to blow out the unit with an air compressor. I put it back in and it worked without that loud noise. I noticed it was much easier to take out the fan/motor with the glove box unit completely removed.