My heater fan blower was making an awful racket, shaking the whole car at highest speed and I wasn't getting any airflow. So I figured it was going bad, and that I needed to replace it.
I got a great deal on one from Hattori Hanzo who pulled it from a wagon he was parting out, and shipped it right away. Pulled the old one and found this:

A bunch of leaves and straw and stuff - and yes, it is off balance by a lot. I think it was somebody's nest.
Anyway, dumped it out, pulled what I could out of the vent, and put it back in. Quiet and good airflow.
So now I need to put this other blower motor up for sale, I guess....