Hi,
Our Maytag Performa washer has developed a problem that seems to be getting worse.
Everything works fine except for right after it fills the tub for the rinse cycle and
normally, would spin the tub to eject the water, there is a humming coming from the
washer, nothing moves, and after a few seconds, it shuts off. If you wait a few seconds,
manually stop the cycle with the control button and start it again, it will them kick in
and continue the cycle, and the rest of the other cycles.
It has done this 3 times and each time (it's getting worse), there is a electrical burning smell. I removed the
front panel of the washer and the motor was pretty hot to the touch. I thought it might be
the starter windings in the motor, so I replaced the motor, but that didn't make any
difference and it still makes the humming and will not continue the cycle unless you do the steps outlined above.
It is not the belt. I removed the belt and tested it and it still does it. While watching the motor and operating the control knob, when you turn it on, the motor will
quickly rotate just a touch, them stop and hum. If you repeatedly turn off/on the control
knob, sometimes there's a click, then the motor starts up. No click = the motor hums. The
humming and the click are both coming from the motor and not from the control knobs area
up on top. It sounds to me like some sort of relay or switch is sticking or not operating.
Like I posted before, I tried a new motor (as in brand new, not rebuilt) and it did
exactly the same thing. Any ideas?
Thanks!

It could be a bad timer (the timer may have a corroded contact, not letting full voltage through to the motor.) or a corroded connection.

Thanks for the response.
How would I go about checking that? The control knob box is plastic and seems to be pretty much sealed. The humming comes from the motor itself - both the old one and the new one.

Well, I've been tinkering with it and it ONLY 'stalls' and hums right after filling the tub for the rinse cycle and then going into the drain cycle. All other cycles operate normally. With my wife operating the control knob, I took a small piece of wood and 'helped' the motor turn the belt while it was humming. As soon as I started pushing on the belt, the motor started. This is starting to really aggravate me since it does this with a new motor as well as the old one. Is there anyway of checking the control knob for proper operation? Thanks again in advance.

1234Aaron:

To explain what the problem is, I'm going to have to teach you a little about electric motors.

Big industrial 440 volt THREE phase motors consist of three different windings in the stator (the thing that doesn't turn) and one in the rotor (the thing that does). Because there is a time lag between the 120 volt power delivered to each of these windings, and they're also arranged equally spaced around the stator, it's EASY to generate a rotating magnetic field with 3 phase power.

The rotor simply follows that rotating magnetic field like a dog chasing it's tail.

It's in fact not too hard to generate something that kinda looks like a rotating magnetic field with only 220 volt power because there's a time lag between the voltage sine wave in one power line and the other.

The problems come when you try to generate a rotating magnetic field with single phase 120 volt power. The problem is that with only a single phase, what you have is an OSCILLATING magnetic field, not a rotating one. That is, if you're looking at an electromagnet in slow motion, the magnetism gets stronger and weaker ( at 60 cycles per second), but it doesn't seem to "rotate" what-so-ever.

That humming noise you hear when the motor is trying to start is the rotor responding to the oscilating magnetic field.

To make the rotor in an 120 volt single phase electric motor turn to follow the rotating magnetic field of the stator, you have to fool the rotor into thinking the magnetic field of the stator is rotating, and this is typically done in one of three different ways. Depending on the way you choose to hoodwink the rotor, you have a split phase motor, a capacitor start motor, or a shaded pole motor. We won't talk about shaded pole motors here. Unfortunately, all three ways of fooling thr rotor require that we underestand the concept of "impedance"):

If you make a graph with resistance on the horizontal "x" axis increasing to the right, and inductance on the vertical "y" axis increasing as you go up and capacitance on the vertical "-y" axis increasing as you go down, you have a graph on which you can plot "impedance".

Instead of having a single winding in the stator, a 120 volt single phase motor will have two windings in the stator...

BUT

one of those windings will be wound with a much thinner wire than the other, and such a motor is called a "split phase motor", which are commonly found on washing machines and dish washers where the motor reverses direction depending on whether the machine wants to agitate or spin or wash or pump, in the case of clothes and dish washers, respectively.

OR

the two windings will be the same, but one of those windings will have a capacitor wired in series with it, and such a motor is called a "capacitor start motor". And, normally such motors are used where the motor only needs to turn one way, but it requires a high starting torque, such as fridges, freezers, air conditioners, dryers and furnace blowers.

(the third way of doing it is called a "shaded pole motor" which we won't get into here and is used where you don't hardly need any torque at all). I flunked grammer. And spelling.

Now, let's consider the split phase motor:

If we have one winding with a small number of turns of very thin wire, then that winding will have high resistance (cuz of the small diameter wire) and low inductance (cuz of the small number of turns) and will plot way to the right and just above the horizontal on our impedance graph. A line drawn from the origin through this point would be at a 5 or 10 degree angle, say.

If the other winding has many more turns of much thicker wire, it has lower resistance (cuz of the thicker wire) but much higher inductance (cuz of the turns). This winding would plot much lower on the resistance axis, but much higher on the inductance axis, and a line drawn from the origin through this point would be at 45 to 60 degrees, say.

Now, inductance creates a time lag in the development of the magnetic field around the inductor. So, the stronger the inductor, the greater the time lag. That means that our two windings will develop their magnetic fields at different times, and it turns out that the angle between the origin and the two plotted points will be exactly equal to the phase shift in the development of the magnetic field between the two windings.

So, if we have a 40 degree phase shift in the development of the magnetic field between the two windings, and the two windings are physically separated around the circumference of the stator, then the rotor will see what it thinks is a single magnetic field that's rotating. That's because it was strongest in this direction before (Nestor points to one pole of the start winding), but it strongest in this direction now (Nestor points to the adjacent pole of a run winding).

In a "split phase motor", the windings with the small number of turns of thin wire is the START winding, and the winding with the large number of thick wires is the RUN winding.

By reversing the polarity of the power going to EITHER the start or run winding (by simply reversing the leads, that is), we can make the magnetic field appear to turn in the opposite direction, and the result is that the motor will run in reverse, and will be perfectly happy to do so.

In a capacitor start motor, we use the same wire and number of turns, but we simply wire a capacitor in series with one of the windings. Now, there's something called "vector addition" that says that if you're walking backward at 3 mph on an airplane going 500 mph, then your speed relative to the ground is only 497 mph. The same thing holds for inductance. if you have one arrow from the origin going to the plotted induction of the winding, then add an arrow from that plotted point going straight down, the overall effective arrow is one going from the origin to the end of the second arrow.

Since it's easy to create a LARGE time delay in the development of the magnetic field using a capacitor, capacitor start motors generally have very high starting torque.

My understanding is that capacitor start motors can also be made to run in reverse by changing the polarity of the start OR run winding.

But, in both cases (split phase and capacitor start), you only need the start winding in the circuit when the motor is first starting to coax the rotor to turn in one direction or the other. Once the motor is up to speed, the physical arrangement of the start windings in relation to the run windings actually causes the motor to run slower and with less power. So, in both cases, the start windings are cut out of the circuit once the motor is nearing it's operating speed.

SO WHAT YOU NEED TO DO IS:

Look on the wiring diagram, and see if there's a capacitor wired in series with one of the windings in your motor. If there is, I'd suspect that capacitor is kaput.

If there is no capacitor, then if the motor reverses direction, it's a split phase motor. Look on the wiring diagram to find a switch or something that reverses the power connection to the start winding of the motor when the machine switches from wash to dry (and the motor then reverses direction to pump water out of the machine instead of around the machine), and if you find such a switch (and it may be the timer itself) then that's the part that's kaput.

And the thing that gave you the answer (even though you didn't know it) was that by using a stick to get the motor turning one way or the other, YOU were the start winding.

If I'm right, if you would have used your stick to turn it the other way, the motor would have been equally happy to turn that way to please you.

Thank you for such a detailed explaination. I found a wiring schematic taped to inside of the control panel. I understand a little of it and I see a capacitor located inside the motor diagram. It's labled: "Capacitor used with alternate capacitor start motor". If you would like to see the schematic, I could scan it and email it to you.
What puzzles me is that if something burned out or wore out inside the old motor, why doesn't replacing it with a new motor cure this problem. Wouldn't the chances of a new motor having exactly the same problem be unlikely?
FWIW, the new motor part is #35-6671 Model S68PXMDN-1089. I guess it's a reversible motor since it's label says 8.5/7.6 amps, 1725/1140 rpm.
Thanks again.

Wait a tick, are you sure this isn't a two speed motor?
What speed is this washer? 1 or 2? If it is 2 speed, then it seems like you got the right motor in there (make sure the one you got is reversable.) If you got the exact same part number then you should be in good shape there.
Basically like Nestor said, a motor needs a "jump start" Either from a capacitor (now these can be mounted ON the motor, or they can be mounted elsewhere, in the console, on the back panel etc.)
Some motors just use a start winding and a run winding with a centrifugal switch to decide between the two (as the motor is starting, the start winding runs, as the speed picks up, the centrifugal switch flips over and shuts off the start winding and turns on the run winding.) You can here this switch click when you turn on your dryer (it will go hmmm, click) it happens in a fraction of a second.
Now, if the start winding is bad (shorted) the motor cannot start.
Replacing the motor should have fixed this problem.
Now lets get away from the motor for a minute.
Check for a capacitor, it will be a round, likely black "thing" mounted in the console, on the back panel (inside) or mounted directly on the motor. If you find one, then it could be bad.
Make sure all connections are good, clean. Then check the timer. Based on when this happens, I think the problem is in the timer. The timer is the only thing that can pick and choose when the motor runs and when it doesn't

Ok, let's take a step back for second since I don't know all that much about house electricity and 110v motors. If it does have an external capacitor (and I haven't found it yet), and that capacitor went bad, would that make the motor hum or would the capacitor itself hum? Second, how can I tell a 1 speed motor from a 2 speed? This motor has a collar device with tangs on it (inside the casing) that is on the motor shaft. It pivots back and forth about 90 degrees of rotation. It is not spring loaded but has 2 springs on it. Is this some sort of centrifical switch? The electrical schematic has 2 symbols on it that look somewhat like light bulbs on their side and they are both labled 'start-motor'. What is their significance to this problem? Next, by the timer, I'm assuming you mean the control unit that designates what cycle the washer performs. If so, the one on this washer has a plastic body that looks to be glued or plastic welded shut. I'm pretty mechanically inclined, but if I cut this open or find a way for it to be disassembled, will it go "sproing" and pieces fly all over, or can I expect a mechanical device that can be examined and repaired?
Thanks.

I just re-examined this washer top to bottom, front to back. It has no external capacitor as descibed by Kurt above. The only wires in it run from house current power to the timer to the water level control and water temp control to the water valves and to the motor. That's it. All wires and connections look to be in fine shape with no corrosion or looseness.
I guess I'll have to take a shot at dis-assembling the timer, right?

If the capacitor is inside the motor, then you're right. Replacing the motor would mean you'd also have a brand new capacitor.

However, it would be kinda dumb for them to put the capacitor INSIDE a capacitor start motor. If the capacitor were to go, then you couldn't replace it without taking the motor apart. (so, it would be kinda like putting the oil filter INSIDE the crank case)

My sister has a Maytag dish washer. On the wiring diagram for her A310 Maytag dish washer it shows a capacitor beside the motor and says "Cap. 50 Hz only", which tells me that they use the same motor on the models sold in Europe, but the ones in Europe ALSO have a start capacitor wired in series with the start winding (for higher starting torque, maybe).

So, if your diagram says "capacitor for alternate capacitor start motor", what that most likely means is that the alternate motor put into models destined for Europe (which uses 220 volt 50 hz single phase power) will have a capacitor fastened to the side of it (so that you can replace the capacitor on that motor without taking it apart).

But, that means if your motor doesn't have such a capacitor sticking out the side of it, it's almost certainly a split phase motor, and there has to be some means of switching the polarity of the power going to the start winding (pronounced "reversing the leads"). Since the motor starts fine some of the time, you know the start winding itself is working fine. And that casts the spotlight of suspicion on the thing that changes the electrical connection to the start winding to reverse the direction of rotation of the motor.

And, what I'm thinking is that switch isn't doing it's job. Instead of switching the polarity of the start winding, it's just going half way and disconnecting the start winding leads, BUT NOT reconnecting them to the opposite terminals. And the result of that would be a motor trying to start with NO START WINDING. (pronounced "oscillating magnetic field")

Do this:

Use aligator clips to connect the leads of a volt meter to the wires going to the start winding of your motor. You should be able to tell which wires those are because the schematic will normally label the start and run windings in the motor.

Set your washing machine to run, and when it gets to the part where the motor just hums, look at your volt meter while it's humming and see if there's 120 volt power getting to the start winding.

I'm willing to bet dollars to donuts there isn't, and whatever part is supposed to be "reversing the leads" going to the start winding is disconnecting them, but not reconnecting them.

On the schematic for the dish washer, does it also have a "timer chart" showing black bars indicating what contacts in the timer are closed during each time increment of the wash cycle? If so, then you should see two columns to the left of that chart labeled something like "contact made" and "contact number".

The contact number will be molded right into the plastic of the timer beside each set of contact points. You should see depictions of those contact points scattered all over your wiring diagram. (On my sister's Maytag A310 dish washer schematic and timer chart, the contact number is circled on both the timer chart and the wiring diagram.) You can therefore tell which contact on the machine's timer corresponds to which of the contacts depicted on the wiring diagram. The timer chart will also have these contact numbers circled.

The schematic will most likely also have non-circled numbers indicating individual electrical terminals (at the ends of wires) inside the dishwasher. When a timer contact closes, it will make a connection between those two electrical terminals (cuz their respective wires both go to the timer). So, on the timer chart, for each contact number on the timer there will also be an entry under "Contact Made" indicating which two electrical terminals inside the machine are being connected.

Look at your timer, timer chart and wiring diagram, and you should be able to figure out where to connect the leads of a voltmeter to measure the voltage across the start winding of your motor.

Then, it's simply a matter of testing to see if there's 120 volts across that start winding when the machine is doing it's buzzing thing.