Mark wrote:
On Mar 30, 6:36 pm, Jerry Trumball wrote:
Boden wrote:
Jerry Trumball wrote:
Boden wrote:
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
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.
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.- Hide quoted 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

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.