At 10:06 AM 2/16/2010, Paul Guzyk wrote:
>is this the motor going?   or a plenum problem?  sound doesn't
>change much if I move heater levers.
>
>http://www.youtube.com/watch?v=iE4Ex_X3mqA

Dear Paul,
I'd like to hear how it sounds when you start it up on speed 1
instead of jumping right to 3, but I'd be very surprised if it isn't
bearing chatter, where the bearing bore has gotten both dry and big
enough that the shaft rolls around the inside of the bearing instead
of spinning smoothly in it.  This takes huge amounts of energy so the
motor never gets up to speed, and makes that gosh-awful noise.  Cheap
power tools do this all the time -- I seriously think that some of
those bearings have a design life of one or two operating hours --
and you can nurse them along for quite a while by applying heavy oil
at each use, but you can't do that here, and you won't get any use
out of it while it's chattering.

As Jim said, the instant start is significant.  If it's bearing
chatter I'd expect to see sharply reduced air output as well.  If it
is, because of the difficulty of access the only sensible thing is a
new bearing, which presumably means a new motor.  But Karl
Mullendore's hole-in-the-sheet-metal trick might get you through the winter.

Yours,
David
ps -- Having recently seen -- and heard -- how Ringling Bros train
their elephants, I have to wonder if your motor hasn't been replaced
by a very small elephant who's being trained to the job. :-(