Need help repairing electric motot

[PSI]

My faithful oscillating fan has given up the ghost. I know I can
go buy a new one but I like tinkering and fixing things so I'm looking
for some help.

The facts:

1) Its a three speed table fan with thermal protection that is about
20 years old.

2) There is no hum indicating its trying to spin and giving it a hand
doesn't help.

3) I removed the capacitor and tested with a multi-meter on the ohm
range. The "resistance" increases steadily to a large number and then
goes to zero ( its a 4 uf 230V cap ). I think this means its OK??

4) There is a "device" in the circuit coming from the neutral to the
cap (ie . white---> "device" ---> cap ). Its tied with string on top
of the winding and inside a clear plastic sleeve, is cylindrical in
shape with one end pointed and coloured orange. There are some
markings on it but I can't read them without removing it first). The
AC voltage before the "device" is 115V. Voltage after the " device"
is 11V.

Is this the thermal-protection? If so does this indicate it's fired
and should be replaced? ( I haven't tried to bypass it because it
means snipping some more wires)

5) Near as I can tell there arre no "brush's " but I haven't fully
dissasembled ( because I don't figured how to get some of the parts
off


Most important: I'm reasonably handy but my electronics/motor
knowledge is basic high-school level( ie I know what a stator,
rotor,armature,commucator etc. are but not sure I can relaibly tell
you if its a split-phase, or induction etc type motor )

Any suggestions are appreciated

Frank

 

[Wayne Tiffany]

The device inside tied to the windings is, indeed a thermal fuse. Sometimes
they open for no apparent reason - no indications of excessive heat. To see
if that's the problem, either check it continuity or jump across it and see
if the fan runs. If it's open, you then have the decision to make as to
whether or not to run the fan without the protection.

WT

 

[Sam Goldwasser]

My faithful oscillating fan has given up the ghost. I know I can
go buy a new one but I like tinkering and fixing things so I'm looking
for some help.

The facts:

1) Its a three speed table fan with thermal protection that is about
20 years old.

2) There is no hum indicating its trying to spin and giving it a hand
doesn't help.

3) I removed the capacitor and tested with a multi-meter on the ohm
range. The "resistance" increases steadily to a large number and then
goes to zero ( its a 4 uf 230V cap ). I think this means its OK??

4) There is a "device" in the circuit coming from the neutral to the
cap (ie . white---> "device" ---> cap ). Its tied with string on top
of the winding and inside a clear plastic sleeve, is cylindrical in
shape with one end pointed and coloured orange. There are some
markings on it but I can't read them without removing it first). The
AC voltage before the "device" is 115V. Voltage after the " device"
is 11V.

Is this the thermal-protection? If so does this indicate it's fired
and should be replaced? ( I haven't tried to bypass it because it
means snipping some more wires)

Yes. If you measure across it with an ohmmeter (fan unplugged!!!),
it is now open.

5) Near as I can tell there arre no "brush's " but I haven't fully
dissasembled ( because I don't figured how to get some of the parts
off

These usually use a shaded pole induction motor, or possibly since you
mention a capacitor, capacitor run induction motor. No brushes.

Most important: I'm reasonably handy but my electronics/motor
knowledge is basic high-school level( ie I know what a stator,
rotor,armature,commucator etc. are but not sure I can relaibly tell
you if its a split-phase, or induction etc type motor )

There are plenty of Web sites with basic motor info.

Your motor may have failed due to gummed up or worn bearings and overheating,
a winding short and overheating, just a tired thermal fuse, etc.

What I'd probably do is confirm the thermal fuse is open and bypass it for
testing. Also check for mechanical problems. To be doubly safe during
testing, consider placing a light bulb in series with the fan so that if
it has a serious short, you won't smoke anything beyond the fan motor.

More info in the small appliance repair guide at the site below.

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Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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[Richard]

My faithful oscillating fan has given up the ghost. I know I can
go buy a new one but I like tinkering and fixing things so I'm looking
for some help.

1) Its a three speed table fan with thermal protection that is about
20 years old.

So it does have thermal protection

2) There is no hum indicating its trying to spin and giving it a hand
doesn't help.

and probably the field coils are not activated

3) I removed the capacitor and tested with a multi-meter on the ohm
range. The "resistance" increases steadily to a large number and then
goes to zero ( its a 4 uf 230V cap ). I think this means its OK?? Yes probably
4) There is a "device" in the circuit coming from the neutral to the
cap (ie . white---> "device" ---> cap ). Its tied with string on top
of the winding and inside a clear plastic sleeve, is cylindrical in
shape with one end pointed and coloured orange. There are some
markings on it but I can't read them without removing it first). The
AC voltage before the "device" is 115V. Voltage after the " device"
is 11V.
Is this the thermal-protection? If so does this indicate it's fired
and should be replaced? ( I haven't tried to bypass it because it
means snipping some more wires)

Yes I have repaired such a motor by replacing the thermal protection
you could verify this by bypassing this device. This of course if
there is no evidence of shorts or burned coils. The thermal protection
is there to prevent over temperature conditions in the coil usually
due to shorts and or course over temperature means more shorts and
possible fire!

5) Near as I can tell there arre no "brush's " but I haven't fully
dissasembled ( because I don't figured how to get some of the parts
off

no these are induction or shaded pole motors, no brushes

 

[PSI]

Replaced the "device", which I now understand is correctly called a
thermal fuse, cleaned out the dried grease and dust, applied some
"electric motor oil" to the shaft and the fan is blowing again -
maybe another 20 years.

Thanks to everyone for the help.

Frank