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About the machine:

Brand: Whirlpool
Model: WDTA50SAKZ0
Warranty: Expired 4 months ago

I bought and installed the dishwasher (brand new) about a year and 4 months ago. Up until 3 weeks ago, I did not have any problems with it what-so-ever. One afternoon, I went to unload the dishwasher to discover the dishes were still dirty. At first, I thought maybe it hadn't been started; however, the soap dispenser had opened and leaked down the door. The soap was still concentrated, so I don't think it sprayed water at all during that cycle.

I restarted the dishwasher and stayed within earshot. I heard the drain pump kick on, but nothing sounded unusual. After the drain cycle, it began filling with water. When it was about half full, I could hear the wash pump start to buzz. The buzzing ramped up quickly and stopped with the sound of a switch clicking off. The sound seemed to have come from underneath the unit. I immediately hit Cancel and it drained and shut down. I secured the power and water, then pulled the unit from under the countertop.

I could tell something was wrong right away. I went around to each motor to make sure the plugs were seated correctly, starting with the wash motor. There was an odd smell coming from the unit. It reminded me of the smell of a hospital. I reached for the plug and discovered that was a bad idea. The wash motor was incredibly hot. I pulled my hand back before touching the motor. It seemed like it was hot enough to cause burns if I had touched it.

I gave the wash motor time to cool and decided to remove the pump to check the range of movement. Much to my surprise, the impeller moved freely. I pulled the service manual to check the specs, which described resistance between 7 - 15 ohms. I confirmed it was within spec, reading at 9.98 ohms. I put it all back together and checked the connectors underneath and made sure the connector's contacts were tightly gripping the contacts on the wash motor, then I leveled the unit and entered diagnostics mode.

I checked for codes by pressing the 3rd key while in diagnostics mode. There was only 1 code: F7 E1 I looked it up in the service manual... wash motor failure. I cleared the code and tried to run a cycle. It started off draining for about 45 seconds, then began filling with water. I heard the wash pump turn on, but it wasn't buzzing like I heard before. About half way through filling, it did it again -- a buzz that started light and ramped up before clicking and shutting off. I let the dishwasher continue its cycle anyway. When it was complete, I secured power and water again. Same as before, the motor was much hotter than it should be, and the hospital smell came back. At this point, I'm assuming the weird smell is the burning of the resin on the transformer wire.

Initial thoughts pointed to the motor not getting enough power. I metered the wires at the motor while running diagnostics. When the cycle first began, it read 125V. I could tell the motor was getting voltage through the vibrations in the test leads, but it didn't seem like it was spinning. I waited for the signature buzzing noise. During the buzzing noise, the voltage dropped to 123V until thermal protection enabled, then it went back up to 125V, but the motor was definitely off. I checked all the other motors and the heater, all of which returned good voltage and resistance values as described in the service manual.

I picked up a "new, open box" motor on eBay. It arrived a couple days later. Before introducing to my dishwasher, I did a resistance test (9.06 ohms) and made sure the impeller spun by hand. It required about the same effort to turn as the original. I installed it, ran a cycle, and same thing -- it got hot, smelled like a hospital, and ultimately did not spray any water. Out of curiosity, I grabbed a meat thermometer, and the motor casing got up to 323ºF!

By this point, I'm thinking maybe the housing is interfering with the impeller's motion (i.e. maybe the plastic warped or something). I went online and decided to order the entire sump, brand new this time. I installed it when it arrived a couple days later, and the exact same symptoms.

It doesn't seem likely that 3 motors have the exact same issue. I found some forums that describe similar issues, but replacing the wash motor fixed the issue for many people. I moved on to other areas, like checking the wiring throughout the machine, checking the connectors and contacts, and performing a continuity test on the wiring itself in case there's additional resistance somewhere. I came back with nothing.

I took the control board out, took a look around and tested some of the components on the board. The service manual mentions checking the triacs, indicating that the triacs control a majority of the high voltage components, so if one thing is working (i.e. the drain motor), then the triacs should be OK. It also described the two fuses, one inline with the neutral, the other inline with the live. I performed the test of checking continuity between P5-1 and P5-4, and they tested OK. I checked the fuses individually, they tested OK. The only things that tested under spec were the two electrolytic capacitors on the board; however, they were definitely within 5% of their labeled values. After tracing the circuit, I don't think these caps influence the wash motor circuit. I also tested the relays on the board by desoldering and checking continuity of the pins while triggering with 12VDC on a bench. Everything looks good on the board.

With everything testing OK, I took one of the 3 motors and connected a test cable to the contacts on the motor, put it in a vice, and powered it up just for a couple seconds. It made noise, but it didn't spin. The impeller just jittered back and forth as if it didn't have enough power to start. It also began warming up just like it does in the machine. I didn't keep it on long enough to tell whether it would get as hot or if it would trip thermal protection, but I think if I kept it on long enough, it would probably reach that point.

At this point, I'm out of ideas. I am thinking there's something wrong with the electric service in the house, but all the tests I've run appear OK. The outlets are at 125VAC, 59.9Hz, tested multiple circuits in the breaker box (kitchen (20A), garage (20A), and dishwasher (15A) breakers).

I've tossed the idea of buying a new control board since I can't get the motors to start properly when directly hooked up. Am I overlooking something obvious? I find it unlikely that 3 motors are bad.

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  • 1
    TL;DR how is the capacitor doing
    – Traveler
    Nov 13, 2022 at 2:17
  • The centrifugal switch that should turn off the Start capacitor is not working
    – Traveler
    Nov 13, 2022 at 2:37
  • There is no start or run capacitor on this model. Here is a link to the service manual static.appliancesconnection.com/attachments/D5f774d6c5d970.pdf Nov 13, 2022 at 3:20
  • 1
    Thank you for the manual. It say there is 25 uF capacitor
    – Traveler
    Nov 13, 2022 at 3:40
  • 1
    3/17-12 Test the capacitor
    – Traveler
    Nov 13, 2022 at 3:46

1 Answer 1

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From the manual:

Manual

  1. Test the wash motor capacitor.

NOTE: A faulty capacitor may cause the motor to "hum", not start, or start slowly.

A. Discharge the capacitor by touching the leads of a 20,000 ohms resistor to the two terminals.

B. Disconnect the wires from the capacitor terminals.

C. With an ohmmeter, measure across the terminals and note reading. If a steady increase in resistance is noted, capacitor is good. Replace wash motor assembly and retest. If the capacitor is either shorted or open, replace capacitor and retest. If the preceding steps did not correct the wash motor problem, replace the control board.

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  • @manassehkatz-Moving2Codidact at lest you found one of the many missing socks
    – Traveler
    Nov 13, 2022 at 5:25
  • This wash motor is the Global Wash Motor SSM, the procedure is found on page 3-18. The wash motor only has two terminals. There is no alternate winding on this model. Nov 13, 2022 at 5:29

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