Sunday, July 19, 2015

Dishwasher Fixn's

So, early June our Frigidaire dishwasher decided it's scrubbing days were over.  When we turned it on, we could hear water go in, it would sort of stagnate with making noises, and then we could hear the drain pump kick on.  Dishes seemed to be a little wet, but the length of cycle was way short, the noise was wrong, and our dishes weren't even close to clean.  We tried a few more runs, and each time we were getting the same (maybe even worse) results.

So like normal Americans, we just called a repair guy and paid $200.

I'm so funny.  Okay, no, we're not normal.  Of course we tried to DIY it.  What harm could it do?

Jon did most of the work on this one, since it he was most vested in the whole dish-washing thing (though I chipped in a bit when the dishwasher was benched)... and it required some heavy lifting.  Although, Jon said it was way lighter than he expected.  So, heavy for my pregnant self, I guess is what I mean.  It is just a big empty tub.

Okay, so the first thing, pretty much right away, was taking off the bottom panel and check for leaks.  We also checked that there were no leaks under the sink.  We had no leaks, which was great news.  No one likes water damage.

The next part was checking that that we could feel the water in the water pipe (under our sink) go from cool to hot when the dishwasher turned on.  It did, which meant it was drawing hot water fine.  Didn't tell us much about the fill rate, but it confirmed what we were hearing.  Water was heading in there.

From there, Jon started cleaning everything he could, just in case it was a nice and cheap clog.  He did the basic cleaning inside the tub, but didn't find much. Then took out one of the few accessible parts from the front, the inlet "water switch" to clean it. He did find a lot of buildup of mineral deposits and was hopeful cleaning those out would fix it for free.  He put it back in.... Nope.  Sad trombone.

Then, life got in the way (okay, we probably were just working on other projects) and we let the dishwasher sit for a week. Once we had a weekend, things got real.  We took that bad boy out.

At this point, we had done a little a googling, and found that of all the components that were in the dishwasher (actually not many), the motor that pumps the water was the most likely failure point.

So, as indicated by the red arrow above, we pulled it out to see if we could see anything (it's not in the picture above).

And a ton of black power came pouring out of the end.  We quickly stuck it it in a nearby recyclable jar.

You can see the powder below.  So that was the first sign it something was up.  We thought maybe it was graphite, used to lubricate bearings.  But there was so much, we knew that this amount was beyond normal.  Jon checked the electrical circuit with his multimeter, and it seemed to check out okay.  So it did seem more mechanical than not.

At this point, we probably could have ordered the part with some confidence, but it was the most expensive part in the whole thing (around $130 OEM), and we wanted to be sure.

And I'm super curious.

So we started disassembling it.  There was a cover for the back side, the one outside the dishwasher that was leaking powder.  It came off easy.  Along with a lot of powder.  My thought was that black impeller was just for cooling.  It's attached on the same bar as the white impeller on the other side that pushes the water through the machine.

Fun fact, my job is in manufacturing super high performance impellers (in metals, of course) for cars, trucks, airplanes and rockets.

So this is where I got really confused and show my ignorance when it comes to some basic mechanical devices.  So much for my mechanical engineering degree.  (Okay, they don't actually teach this stuff in college). I rocked differential equations though.

The bearings, as far I could tell, didn't use graphite.  So I started googling what that black powder could be. One of the comments on this video about powder led me to watch it.  It is an amazingly helpful video.. and answered all of my questions without having to take apart the whole thing, and likely injure myself... and others.

He said that there were carbon brushes for the motor, and those wear down over time.  I knew how a motor worked in theory... but not in practice.  Led me to more youtube gold.  I searched for"brush motor".

Okay, so now armed with science, I looked back at our motor.  Our motor looked just like the video, two brushes, commutator, coiled wire, etc.

The brushes, however were really worn, and worn unevenly.  One side had almost no carbon left, and the spring was extended a lot (less force).  The red below is the holder for the brush and the "good" brush.

When I looked at the "commutator", it had an odd contour to it.   Didn't seem to be by design, so I thought maybe that was worn too.  

So now it all made sense. The black powder was actually 'graphite', in that it was ground up carbon. We expected that commutator was worn as well as the brushes, we decided not to be super cheap about it, and instead of ordering nice cheap $5 brushes, but just went ahead and ordered the replacement part.  We found amazon had the best price at $80, and free shipping (Yay amazon!), so we ordered it. 

And then we waited.  And waited.  Five days shipping seems like a long time when you're washing dishes by hand... and have this thing sticking out in your kitchen.

In the meantime, I gave the kids a lesson on motors :)  I showed them the video and had them take a look at it to see if they could troubleshoot the problem like we did.  Nothing like good teaching moment, right?

To wrap it up, the part came, Jon put it in quite uneventfully.  Looking it over, the commutator was supposed to be straight, so I am glad we got a new motor.  He hooked it all back up and by the time I got home from work... the dishwasher was on its second load!  One thing we noticed too, our dishwasher actually had more cleaning power because the motor was new and working well.

Happy ending for everyone!


Kelly said...

It's good that you were able to fix yours. When our motor broke, we did some googling and found the part was almost as expensive as the dishwasher cost when it was new. No joke. The MSRP of the dishwasher was originally $269. That explained a lot.... like for instance what a piece of junk it was in every way.

Cassie said...

Yeah, I had looked the price of comparable new ones just to put the cost of the part into perspective. We're still very happy with ours, and didn't see much advantage of a new one.