Puddin' Man wrote:
On Mon, 09 Apr 2012 17:31:39 -0700, wrote:

Michael A. Terrell wrote:

Puddin' Man wrote:

(...)

Purchased ~ 4 years ago.
Used extensively mostly in summer of 2011 (maybe 10 hours/day).
Made strange sympathetic vibration sound, ~C#.

'Sounds like a failed bearing.

I doubt it. It made that sound all summer. No evidence of a burnt
bearing. No play in the fan shaft.

Worked OK about 3 weeks ago.
Stopped functioning altogether.

The shaft turns freely. No evidence of a heat problem.
Gets 120v thru feed wires.

As Michael mentioned, presenting 120 V to the coil does
not necessarily mean there is current through the coil.

Understood.

No contacts on coil (cannot test voltage there).
Just sits there and looks dumb when powered.

Can't find -any- specs on it (Model MH-20UL)

Chinese wonder mystery, probably not worth further consideration?

'Probably true. Please use your multimeter to measure the resistance
of the switch when on, wires, connectors etc.

As Michael implies, your first - order test would be a resistance
measurement from prong to prong on the unplugged A.C. connector.

If it is 'open' and the switch and power cable tested OK, you're
probably not going to be able to repair the motor economically.

Such is the case.

It is your call whether you want to unwrap the winding to discover
an open fuse as a matter of edification and entertainment,
before you throw it away.

If you are really economical (as I can be), you can salvage a low-
mileage shaded-pole motor out of a scrapped microwave oven and
use that in your fan. I see four in my scrap box from where
I'm sitting!

Shaft adapters are left as an exercise.

All of that is well beyond me.

I don't even know how to properly test because I
don't understand the wiring. :-(

Series circuit. AC hot to switch, from switch to motor,
from motor to AC neutral, pretty much.
That is what you see, yes?

Spare a minute? I comprehend that I can wrap wires around a conductor, apply
current, and have an electromagnet. If I can time the switching of polarity,
and place the em in the field of a fixed magnet, I'll have basic components
of an elec. motor. No?

See below.

Alternatively, I could have + and - fields formed with the em, and have a
fixed magnet as an armature (??) thus constituting a "motor".

But I'm still miles from understanding how this shaded pole motor works.
It looks like it has a big fixed magnet (but with copper tubes running
around it), a large winding presumably between the N and S poles, and
a separate armature (with fan shaft) in the middle of the fixed magnet.
This describes what I see in the pics.

If you can explain how these components relate to my miniscule understanding
of the basic components of a "motor" (above), I would award you with a
(virtual) "Cigar And A Beer". :-) I'm obviously missing a bunch. Hope I
haven't mangled the terminology too badly.

Please review the results of your Internet
searches WRT motors in general and shaded pole motors
in particular. I expect some have very illuminating
illustrations and perhaps a cartoon or two.

My understanding of these things is marginal
at best, so I hereby bump your question to
those more knowledgeable and articulate.



--Winston