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Home > Archive > Home Repair forum > April 2008 > dryer motor
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| Jerry Trumball 2008-03-30, 5:25 pm |
| I have a GE DDE7208 dryer with a 5KH26JJ motor. When the motor is
stationary, the centrifugal switch energizes the start winding along
with the run winding. When I depress the starter, the motor hums but
does not turn even with the belt off. That points to a bad motor, but I
want to be sure.
Winding resistances are 3 and 4 ohms. That doesn't prove the insulation
is holding up at 120 VAC, but if there were a leak so bad that the motor
wouldn't turn even unloaded, wouldn't the overload protector break the
circuit?
At 2 amps DC, there are only 6 mv across the centrifugal switch, so the
contacts appear to be fine.
Bearings have no slop or noise but more friction than some motors I've
seen. It takes 0.7 inch-pounds to get the shaft moving.
What could be wrong?
| |
| gfretwell@aol.com 2008-03-30, 5:26 pm |
| On Sun, 30 Mar 2008 14:28:24 -0400, Jerry Trumball <Jer@privacy.com>
wrote:
>I have a GE DDE7208 dryer with a 5KH26JJ motor. When the motor is
>stationary, the centrifugal switch energizes the start winding along
>with the run winding. When I depress the starter, the motor hums but
>does not turn even with the belt off. That points to a bad motor, but I
>want to be sure.
>
>Winding resistances are 3 and 4 ohms. That doesn't prove the insulation
>is holding up at 120 VAC, but if there were a leak so bad that the motor
>wouldn't turn even unloaded, wouldn't the overload protector break the
>circuit?
>
>At 2 amps DC, there are only 6 mv across the centrifugal switch, so the
>contacts appear to be fine.
>
>Bearings have no slop or noise but more friction than some motors I've
>seen. It takes 0.7 inch-pounds to get the shaft moving.
>
>What could be wrong?
Capacitor?
| |
| Jerry Trumball 2008-03-30, 5:26 pm |
| gfretwell@aol.com wrote:
> On Sun, 30 Mar 2008 14:28:24 -0400, Jerry Trumball <Jer@privacy.com>
> wrote:
>
>
>
> Capacitor?
I was sort of hoping for that, but this motor doesn't use one.
| |
|
| Jerry Trumball wrote:
> I have a GE DDE7208 dryer with a 5KH26JJ motor. When the motor is
> stationary, the centrifugal switch energizes the start winding along
> with the run winding. When I depress the starter, the motor hums but
> does not turn even with the belt off. That points to a bad motor, but I
> want to be sure.
>
> Winding resistances are 3 and 4 ohms. That doesn't prove the insulation
> is holding up at 120 VAC, but if there were a leak so bad that the motor
> wouldn't turn even unloaded, wouldn't the overload protector break the
> circuit?
>
> At 2 amps DC, there are only 6 mv across the centrifugal switch, so the
> contacts appear to be fine.
>
> Bearings have no slop or noise but more friction than some motors I've
> seen. It takes 0.7 inch-pounds to get the shaft moving.
>
> What could be wrong?
My experience with motors is that under normal operation windings don't
fail. Usually the problem is with the "stuff" surrounding the
magnetics. Switches, capacitors, bearings, clutches, etc. Make sure
everything is clean and lubricated. The motor may not have much
starting torque so compromised bearings mare be a problem. Can you
safely give the motor a bit of help when starting to verify or rule this
out?
Boden
| |
| Jerry Trumball 2008-03-30, 5:26 pm |
| Boden wrote:
> Jerry Trumball wrote:
>
> My experience with motors is that under normal operation windings don't
> fail. Usually the problem is with the "stuff" surrounding the
> magnetics. Switches, capacitors, bearings, clutches, etc. Make sure
> everything is clean and lubricated. The motor may not have much
> starting torque so compromised bearings mare be a problem. Can you
> safely give the motor a bit of help when starting to verify or rule this
> out?
>
> Boden
Thanks. The switch I push to start gave a consistent hum, but I could
check it with a couple of amps to be sure the voltage drop is tiny and
consistent.
That leaves friction. The 0.7 inch-pounds I measured would be
equivalent to 1 pound of pull on the belt. That doesn't sound like
much, but maybe it was higher before I removed the motor to measure.
One website said removing the motor and vacuuming the dust can sometimes
reduce friction enough to get it working again.
I started the motor several times a few days ago because I was removing
items a few at a time. There was no starting trouble. I wonder if
whatever lubricates the plain bearings got a little gummier since then.
Should I try to lubricate the bearings? I have WD-40, sewing-machine
oil, and motor oil.
| |
|
| Jerry Trumball wrote:
> Boden wrote:
>
>
>
> Thanks. The switch I push to start gave a consistent hum, but I could
> check it with a couple of amps to be sure the voltage drop is tiny and
> consistent.
>
> That leaves friction. The 0.7 inch-pounds I measured would be
> equivalent to 1 pound of pull on the belt. That doesn't sound like
> much, but maybe it was higher before I removed the motor to measure. One
> website said removing the motor and vacuuming the dust can sometimes
> reduce friction enough to get it working again.
>
> I started the motor several times a few days ago because I was removing
> items a few at a time. There was no starting trouble. I wonder if
> whatever lubricates the plain bearings got a little gummier since then.
> Should I try to lubricate the bearings? I have WD-40, sewing-machine
> oil, and motor oil.
>
WD-40 should not be used as a lubricant. It is not a good long term
lubricant. The other two, motor oil or sewing machine oil are fine.
| |
| Jerry Trumball 2008-03-30, 8:25 pm |
| Boden wrote:
> Jerry Trumball wrote:
> WD-40 should not be used as a lubricant. It is not a good long term
> lubricant. The other two, motor oil or sewing machine oil are fine.
>
That looks like the solution. I measured the friction again, wrapping
the string around the shaft at the blower end, and got 0.5 inch-pounds.
Last night I wrapped the string around the pulley, which is probably
less accurate.
All that friction made me think they were plain bearings. That seems to
be wrong. It's an open-frame motor, so I think I can apply a tiny bit
of "small motor" oil without making a mess.
.... Well, I applied a little oil, spun it, and found that the friction
had risen to 5.5 inch-pounds. Now it's back down to 5. It looks as if
something is funny in the bearings, and the oil may do the trick.
| |
|
| On Mar 30, 6:36=A0pm, Jerry Trumball <J...@privacy.com> wrote:
> Boden wrote:
>
>
>
>
>
>
>
[color=darkred]
ure[color=darkred]
>
>
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>
>
[color=darkred]
>
>
> That looks like the solution. =A0I measured the friction again, wrapping
> the string around the shaft at the blower end, and got 0.5 inch-pounds.
> =A0 Last night I wrapped the string around the pulley, which is probably
> less accurate.
>
> All that friction made me think they were plain bearings. =A0That seems to=
> be wrong. =A0It's an open-frame motor, so I think I can apply a tiny bit
> of "small motor" oil without making a mess.
>
> ... =A0Well, I applied a little oil, spun it, and found that the friction
> had risen to 5.5 inch-pounds. =A0Now it's back down to 5. =A0It looks as i=
f
> something is funny in the bearings, and the oil may do the trick.- Hide qu=
oted text -
>
> - Show quoted text -
put the belt back on, open the door, hold the door button in, press
the start button and spin the dryer by hand to see if that will start
it.
Mark
| |
| Jerry Trumball 2008-03-30, 8:25 pm |
| Mark wrote:
> On Mar 30, 6:36 pm, Jerry Trumball <J...@privacy.com> wrote:
>
> put the belt back on, open the door, hold the door button in, press
> the start button and spin the dryer by hand to see if that will start
> it.
>
> Mark
>
Good idea. I wish I'd thought of it before I removed the motor. If the
motor doesn't work when I put it back in, I'll try turning the drum.
Somehow I'll need to press the door interlock and the start switch as I
turn the drum.
Above, I meant .55 and .5 inch pounds. It's going much lower if I pull
the cord two or three times in a row, but higher if I let the shaft sit
a couple of minutes. Maybe the oil needs time to work.
| |
| Jeff Wisnia 2008-03-31, 3:25 am |
| Jerry Trumball wrote:
> I have a GE DDE7208 dryer with a 5KH26JJ motor. When the motor is
> stationary, the centrifugal switch energizes the start winding along
> with the run winding. When I depress the starter, the motor hums but
> does not turn even with the belt off. That points to a bad motor, but I
> want to be sure.
>
> Winding resistances are 3 and 4 ohms. That doesn't prove the insulation
> is holding up at 120 VAC, but if there were a leak so bad that the motor
> wouldn't turn even unloaded, wouldn't the overload protector break the
> circuit?
>
> At 2 amps DC, there are only 6 mv across the centrifugal switch, so the
> contacts appear to be fine.
>
> Bearings have no slop or noise but more friction than some motors I've
> seen. It takes 0.7 inch-pounds to get the shaft moving.
>
> What could be wrong?
Some portions of the motor housing or end caps may have "warped" enough
so the outer surface of the rotor will get pulled into mechanical
contact with the inside of the stator when magnetic fields are present
and then "stick there".
Can you try powering the motor and rotating the pully carefully by hand
and see if it seems "stuck" when power is applied?
Can you disassemble the motor and see if there are any "rub marks" on
the outer surface of the rotor?
I've encountered this phenomena a couple of times over the years.
Let us know what you find,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.98*10^14 fathoms per fortnight.
| |
| Jerry Trumball 2008-03-31, 3:25 am |
| Jeff Wisnia wrote:
> Jerry Trumball wrote:
>
> Some portions of the motor housing or end caps may have "warped" enough
> so the outer surface of the rotor will get pulled into mechanical
> contact with the inside of the stator when magnetic fields are present
> and then "stick there".
>
> Can you try powering the motor and rotating the pully carefully by hand
> and see if it seems "stuck" when power is applied?
>
> Can you disassemble the motor and see if there are any "rub marks" on
> the outer surface of the rotor?
>
> I've encountered this phenomena a couple of times over the years.
>
> Let us know what you find,
>
> Jeff
>
The frame is riveted. Before reassembly I tried looking between rotor
and stator to see if there was dust. The spaces looked even.
After reading your post, I plugged it in and pressed Start. It started
every time. I think maybe oxidation in the damaged stranded wire at the
plug kept the motor from starting, and wiggling the cord has reduced
resistance for now. I'd better get a cord before I try drying laundry.
I have a rattle now. Investigating, I found about 5mm endplay for the
drum. Maybe that's normal. The rattle seems to be coming from the
sheet metal behind the drum, where the heating elements are mounted.
Opening the unit will be much easier this time!
| |
| Stormin Mormon 2008-03-31, 8:25 pm |
| Clean the berrings with a shot of brake cleaner, Gumout spray, or other
areosol solvent. Let it dry throroughly, specially if the spray is
flammable. The proper lube is something like ND 30 (non detergent). Failing
that, 10w30 should give you years of service.
WD and sewing machine oil are totally not suited. They dry and get gummy.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
..
"Jerry Trumball" <Jer@privacy.com> wrote in message
news:8STHj.27708$r76.19673@bignews8.bellsouth.net...
Should I try to lubricate the bearings? I have WD-40, sewing-machine
oil, and motor oil.
| |
| Stormin Mormon 2008-03-31, 8:25 pm |
| I've found 3 in 1 to dry out. I'm not totally sure about sewing machine oil.
Still, I'd choose 10w30 of those choices.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
..
"Boden" <Boden@tidewater.net> wrote in message
news:fsp2j701cqf@enews5.newsguy.com...
WD-40 should not be used as a lubricant. It is not a good long term
lubricant. The other two, motor oil or sewing machine oil are fine.
| |
| Stormin Mormon 2008-03-31, 8:25 pm |
| You are an engineer?
--
Christopher A. Young
Learn more about Jesus
www.lds.org
..
"Jerry Trumball" <Jer@privacy.com> wrote in message
news:yBUHj.37242$by3.21322@bignews5.bellsouth.net...
That looks like the solution. I measured the friction again, wrapping
the string around the shaft at the blower end, and got 0.5 inch-pounds.
Last night I wrapped the string around the pulley, which is probably
less accurate.
All that friction made me think they were plain bearings. That seems to
be wrong. It's an open-frame motor, so I think I can apply a tiny bit
of "small motor" oil without making a mess.
.... Well, I applied a little oil, spun it, and found that the friction
had risen to 5.5 inch-pounds. Now it's back down to 5. It looks as if
something is funny in the bearings, and the oil may do the trick.
| |
| Jerry Trumball 2008-03-31, 8:25 pm |
| Stormin Mormon wrote:
> You are an engineer?
>
No. The bearings had a little more friction than I've felt on some 1/4
hp electric motors. Not knowing why the motor didn't turn when I
pressed the button and whether this much friction was normal, all I
could think to do was get a number by pulling a cord.
Isn't 3-in-1 like 5W motor oil without additives?
I want to cut open the old power cord. I'll bet there a lot of broken
copper strands. I wonder how many dryer cords get like that. I wonder
if they are a fire hazard.
| |
| Jeff Wisnia 2008-04-02, 5:25 pm |
| Jerry Trumball wrote:
> Jeff Wisnia wrote:
>
> The frame is riveted. Before reassembly I tried looking between rotor
> and stator to see if there was dust. The spaces looked even.
>
> After reading your post, I plugged it in and pressed Start. It started
> every time. I think maybe oxidation in the damaged stranded wire at the
> plug kept the motor from starting, and wiggling the cord has reduced
> resistance for now. I'd better get a cord before I try drying laundry.
>
> I have a rattle now. Investigating, I found about 5mm endplay for the
> drum. Maybe that's normal. The rattle seems to be coming from the
> sheet metal behind the drum, where the heating elements are mounted.
> Opening the unit will be much easier this time!
It's likely time to replace the whole cord set, they don't cost all that
much.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
| |
| Stormin Mormon 2008-04-03, 1:26 pm |
| For whatever reason, the three in one oil I've had dries out after a while.
I think it's different.
Broken strands. That's why they have so many strands. So one or two can
break, but the rest keep carrying electric. They break in different places
along the cord.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
..
"Jerry Trumball" <Jer@privacy.com> wrote in message
news:wveIj.16020$%15.8714@bignews7.bellsouth.net...
Isn't 3-in-1 like 5W motor oil without additives?
I want to cut open the old power cord. I'll bet there a lot of broken
copper strands. I wonder how many dryer cords get like that. I wonder
if they are a fire hazard.
| |
| Jerry Trumball 2008-04-03, 5:25 pm |
| Jeff Wisnia wrote:
> Jerry Trumball wrote:
>
>
> It's likely time to replace the whole cord set, they don't cost all that
> much.
>
> Jeff
>
I replaced the cord and cut the old one apart. The wire was fine.
Apparently the trouble was where the the wire was soldered (?) to the
brass (?) spade in the plug. Cutting up that thick rubber plug was
tough enough that I didn't finish the autopsy.
The noise came from the blower's plastic impeller. It turned silently
with the power off sounded as if it were out of balance when the motor
came on. Clamping it a mm closer to the end of the shaft made it
smoother. I don't understand why.
| |
| Jerry Trumball 2008-04-03, 5:25 pm |
| Stormin Mormon wrote:
> For whatever reason, the three in one oil I've had dries out after a while.
> I think it's different.
I used Marvel Lubricating Oil. Its recommended uses include small
motors, but I don't know if 1/4 hp is what they mean by small.
Apparently the bearings were doing fine, so it would have been better to
leave them alone. I don't think enough Marvel got into the bearings to
wash away any original lubricant.
>
> Broken strands. That's why they have so many strands. So one or two can
> break, but the rest keep carrying electric. They break in different places
> along the cord.
>
That seems to happen with things like headphone cords. I think
oxidation can keep current from flowing from one strand to another. In
that case you replace the cord or the headphones.
I found no broken strands in the dryer cord. Apparently it was a bad
connection in the molded rubber plug.
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