Motor Wiring Help Please!

I thought all washing machine motors were DC as its easier to reverse and speed control

Standard north american washing machines have used AC induction motors since the beginning, they're often two speed, non reversible and use a mechanical transmission to drive the oscillating agitator and spin cycle. The last few years European-style front loaders with series wound universal or polyphase VFD driven induction motors are becoming much more popular but the old fashioned induction motor powered top loader is still in probably 95% of homes.

I live and learn I never have lived in America just assumed they were similar the the UK ones

Please recheck your ohms readings. In particular, make sure the 0.4 ohms isn't actually 0 ohms, taking into account the lead resistance. 0.4 ohms could be a winding; 0 ohms or 0.1 ohms is a connection.

With respect to you followup post:

Sounds like a single speed motor. There should be a run winding connection and a start winding connection through the centrifugal switch.

(I'm a bit surprised that the external green wire isn't the case ground, but it wouldn't be connected to anything else.)

My guess would be 1-4 or 1-6 is the run winding with 4 and 6 actually tied together.

If you have a Variac, I'd suggest Hot to 1 and 2, Neutral to 5 and 6. Start at 0 V and bring up the voltage. If you can monitor current, it probably shouldn't go above 2 or 3 amps with no load. The motor should start turning at a relatively low voltage. Take it up high enough for the centrifugal switch to cut out and let it run for awhile, checking that the case doesn't become hot.

--- sam | Sci.Electronics.Repair FAQ:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

It's surprising just how different they are, just recently acquired a Creda front load washer which as far as I know is a very typical UK unit but it was completely new to me and took some exploring to understand how it worked well enough to fix it. I also picked up and fixed a Maytag Neptune which is a high end American made front loader which performs very well compared to the top loaders I've always had. I like the design of the Creda a bit better but it has a much smaller capacity, probably about half. The Neptune is one of those which uses a 3 phase induction motor with an electronic variable frequency drive, pretty cool stuff.

James,

I bought a Neptune washer model MAH5500BWW in 2001. It has been working until this Monday. The motor does not spin at all. BTW, I totally missed out on the class action lawsuit since I hadn't had any problems with the washer. An of course, I don't have the warranty anymore.

So I opened the main control board cover and found a wiring diagram and some diagnostic test instructions. I ran the test and traced it down to the motor control board (located at the lower right bottom from the front panel), and a 10Amp fuse was blown. The instructions states that "If the motor does not run: Check the 10 amp fuse located on the control board, either visually or with an ohm meter. If bad, replace motor control/wire harness assembly completely." I checked the maytag website and the part costs $174.99 + tax + shipping. After reading all the problems with the neptune washer on the net, I am not sure if I want to reinvest about $200 on this thing, which may fail with other problems sooner or later.

With my understanding in electricals, a fuse is supposed to the protect the circuitry. So why in the world do you need to replace the entire assembly if just the fuse is blown. I went to the radio shack and bought a 10 amp fuse, soldered it in, ran the test again, same failure.

With your experience in fixing a neptune, can you shed some light or give me any suggestions. I'd be much appreciated.

Best Regards, PB

Well so far I've picked up two Neptunes, both with the exact symptoms you describe. The first one I was lucky and the fuse was not blown on the motor board and resoldering a bunch of cracked joints got it up and running.

The next one the fuse was also not blown, but several of the MOSFETs, and a couple of the driver chips had craters blown in them. I replaced those parts and then discovered that the large custom chip was also fried so I ended up replacing the motor board, got lucky and a friend had an extra one through a screwup of the warranty service on his but you can order them from repairclinic.com.

You can try replacing any shorted mosfets and driver IC's and you may get lucky, or you may find that the control chip is fried. It's unfortunate that they didn't incorporate any sort of isolation or protection so if a mosfet shorts then high voltage can trace right back into the low voltage logic. The fuse blows to prevent anything from catching fire, but logic chips can be fried an order of magnitude quicker. What I would do is remove any shorted mosfets and their respective driver chips, then apply power and check for 5V across the power and ground pins on the control chip. In my fried one it was holding the voltage down to around 1V. You could also check for signs of life from the outputs of the chip, a scope will help here but be sure you power the board from an isolation transformer if you try that.

Thanks James for lots of useful info.

I further inspected the board and found out that Q5, R34, and R35 are blown. I didn't notice these before. They may have been fried after I installed the fuse. For Q5, I am planning to find one from radio shack. But, I need the resistance values on R34 and R35. Would you by any chance have this numbers?

Thanks, PB

I found more fried parts: Q5, R34 and R35. Do you have any info on the resistance values of R34 and R35?

Thanks, PB

You probably won't find Q5 at Radio Shack, it's a high voltage N-channel power MOSFET, digikey sells the P16NK60Z which will work though. Make sure you test the rest, often they will short without visibly blowing up. On mine one of the big diodes was also shorted, as were a few smaller ones and most of the IR2101 IC's were shorted.

R34 and R35 are 75 ohm. Make sure you check IC8 because it's a custom chip, if that chip is bad then replacing any other parts is a waste of time because you can't get a new IC8. If that does appear to be OK then you'll have to at minimum have a multimeter to test for shorted diodes and transistors, if you miss one shorted part it could very well blow up all the new parts you installed in the blink of an eye. It's just the way it is with power electronics.

Here's a pic I took earlier showing the original motor control board on the right, then on the left is the replacement board along with the strange bucket it mounts in. As you can see, it was completely redesigned.