I just replaced my heater blower a couple of weeks ago.  It had been
making a racket and would only run on high setting for quite a while. Then
it stopped working completely.  I replaced the motor and it still did not
work.  Turns out the switch was fried.  The motor bearings were trashed by
dirt/age causing too much current draw.  Luckily, the $20 dollar fan switch
jumped in and saved the day by melting, sacrificing itself for the 10 cent
fuse.
     Changing the motor was a big job.  I don't want to do it again.

                               John Reddick