Any way to decipher wires on an AC motor?

[Walker]

Wasn't sure whether to put this in the DIY forum or here, but I figure I'll get the attention of more electrically savvy folks here.

My (ancient) dishwasher died. The control board on it fried. It was probably repairable, but it was old and we decided to just replace it.

Being the guy that I am, I totally disassembled it and pulled off every part that I might someday think of a use for. This mainly came down to the motor and a solenoid valve that served as the water inlet.

The thing is old enough that I can't find any documentation for it online. I'm not very versed in AC motors. I motorized my grain mill, but that motor came with a wiring diagram so it was a no-brainer. This one though.... I got little to go on.

The thing has 4 wires (red, yellow, blue, grey), plus ground. The circuit board and wiring harness don't really have anything labeled. I'm trying to figure out how to hook it up to drive it (either CW or CCW, whatever, don't care),.

I thought I got lucky and figured it out based on some wire color information in some old archived usenet post. WHen I tried hooking it up that way, it did indeed start spinning and I thought I was all set, but after about 15 seconds I started to smell and see a wisp of smoke, so I pulled the plug.

Anybody got any tips or ideas? I'm pretty clueless here.

 

[P-J]

Please tell everthing you know about the DW and the motor. Based on what you note, it seems like it might be a cap start/run motor.

Let me know and I might be able to figure it out. (Hey - I studied motor winding before you were born. Really.)

 

[Walker]

Three attachments.

snap of DW model (maytag).
From what I was able to find, the motor is branded as whirlpool.

snap of motor label included.
Note that the DW label says the motor is 5.5A, but the motor itself says 6.5A.

snap of harness connected to motor. resistances I measured on the pins of the motor:

blue <-> grey: 7.5 Ohm
blue <-> red: 7.5 Ohm
blue <-> yellow: 3.5 Ohm

grey <-> red: 14 Ohm
grey <-> yellow: 10 Ohm

red <-> yellow: 10 Ohm

Once those 4 wires hit the control board, it becomes a matter of reverse engineering the routes and components on the PCB to see what is connected to what. I didn't do any of that work (yet). Not sure if I am that motivated. Hell, I might have fried the thing already anyway.

 

[P-J]

That is a complicated little devil. The best that I can figure is that it is a reversable motor so only 3 of the 4 wires would be powered at any one time. I also think it might be a capacitor start motor. Is there a motor start cap anywhere in the circuit?

It appears that the yellow & blue wires are the run winding. Then the yellow & red OR the yellow & grey would set the direction of rotation.

It's all a guess at this point though.

Still scratching my head.

P-J

 

[Walker]

That is a complicated little devil. The best that I can figure is that it is a reversable motor so only 3 of the 4 wires would be powered at any one time.

It is reversible. As I took it all apart, I noticed the way the pump impeller(s) were built. It was actually pretty slick if I understood it right. If the motor rotated in one direction, the pump would circulate and spray the washing water around. If it was rotated the other direction, the pump would suck the water out of the main housing and jettison it through the drain hose.

I also think it might be a capacitor start motor. Is there a motor start cap anywhere in the circuit?

There are several capacitors on the circuit board. Most are tiny, but couple of them decent sized (think thimble) that are possibly there for start and/or run. But like I said, I didn't try to reverse engineer the board (yet).

It appears that the yellow & blue wires are the run winding. Then the yellow & red OR the yellow & grey would set the direction of rotation.

It's all a guess at this point though.

Still scratching my head.

P-J

Cool. Even guesses are better than nothing.

I have no problem experimenting on this thing. If I nuke it, it goes in the garbage and I move on with my life.

 

[Walker]

It appears that the yellow & blue wires are the run winding. Then the yellow & red OR the yellow & grey would set the direction of rotation.

If that is the case, it would mean that one of the wires was totally unused, wouldn't it?

Yellow is involved in both run and direction functions.

Blue involved in run.

If red is involved in direction, grey is unused.
If grey is involved in direction, red is unused.

edit: perhaps the thing has two speeds?

 

[P-J]

There are several capacitors on the circuit board. Most are tiny, but couple of them decent sized (think thimble) that are possibly there for start and/or run. But like I said, I didn't try to reverse engineer the board (yet).

A start cap would be fairly large. With what you describe it probably does not use one.

Give it a try when you get a chance.

P-J

 

[P-J]

If that is the case, it would mean that one of the wires was totally unused, wouldn't it?

Yellow is involved in both run and direction functions.

Blue involved in run.

If red is involved in direction, grey is unused.
If grey is involved in direction, red is unused.

edit: perhaps the thing has two speeds?

Missed this post (we both responded at the same time)

I don't think it is 2 speed. I believe your first summation correct.

 

[reynolds5520]

http://www.appliancepartspros.com/07-wiring-information-parts-for-maytag-mdb5100awb.html


The last digit in the model number usually identifies the color of the paint - this should be the right diagram.

 

[P-J]

That is a complicated little devil. The best that I can figure is that it is a reversable motor so only 3 of the 4 wires would be powered at any one time. I also think it might be a capacitor start motor. Is there a motor start cap anywhere in the circuit?

It appears that the yellow & blue wires are the run winding. Then the yellow & red OR the yellow & grey would set the direction of rotation.

...

With reynolds5520's post, the wiring info I guessed at is a little wrong.

The Blue wire is the common (not the yellow) and indeed the Blue & yellow together makes the run winding. The Blue & grey set one direction and then the Blue and red sets the reverse direction.

 

[P-J]

...
The Blue & yellow wires are the run winding. Then the Blue & red OR the Blue & grey would set the direction of rotation.
...

If that is the case, it would mean that one of the wires was totally unused, wouldn't it?

Blue is involved in both run and direction functions.

Yellow involved in run.

If red is involved in direction, grey is unused.
If grey is involved in direction, red is unused.
...

I reworded the set up. Hope this makes it more clear. Sorry for my mistakes.

And a huge thanks to reynolds5520 for setting me straight.

Edit: Here is the motor wiring/connection diagram:

P-J

 

[reynolds5520]

Happy to give a little back!

 

[Walker]

AWESOME SAUCE!

Thanks. I looked and looked and looked and could not find wiring diagrams.

 

[Walker]

OK, motor works, but I did smoke it again in the process.

Like I said before: I am not in my element with motors.

Seems I have to energize the run winding and then just give it a very brief momentary tap on the forward or reverse wires to get it started.

After that, forward and reverse leads can be left floating.


That sound about right?

 

[Shockerengr]

A start cap would be fairly large. With what you describe it probably does not use one.

Give it a try when you get a chance.

P-J

As a small motor, it's probably using smaller guage wires to increase the resistance to create the rotating field to start rather than a capacitor.

That's why they tend to smoke when people try to run them using the start coils rather than the run coils.