I Can't Sleep When Things Are Broken, a Dishwasher's Story

One night, about a year ago, I started my dishwasher before going to bed. It has a few steps it goes through when you turn it on: pump out the old water, let frsh water in, then once the water is high enough, turn on the recirculating pump and start washing. So I hit start and lay down in bed. It's pretty noisy, but it's white noise. About one minute after laying down, I'm almost unconscious when I'm right back alert. No sound. Hmm, maybe I fell asleep and didn't notice. I check the dishwasher: everything's dirty. Okay, put more detergent in and start again; who knows, maybe I imagined the whole thing. I go back to bed, but listen this time. Silence again. Why?

This escalates to me having the dishwasher torn apart, parts and tools strewn about the kitchen. Screwdrivers, multimeter, and jumper wires at my disposal. I reverse-engineer the wash cycle, using the manual and the parts at hand to reason out what it is supposed to do. Water is everywhere while I'm wrapped around and probing 120V wires -- at least it's plugged into a GFCI outlet.

I eventually figure out the motor is supposed to be pumping the hot water -- crap, motors are expensive. It has a funny power arrangement, 3 power wires (ignoring starter/run stuff). One is neutral, of course, but the other two run to the control board. I jab a jumper wire and connect both to 120V hot. It makes horrible noise! That's better than silence. A few minutes later and I reason out you apply power to one wire when you want to discharge water to the sink and the other when you want to pump it into the sprayer. And the motor works perfectly when I do that! Now we're down to the control board, fortunately my expertise :).

So I'm not measuring any voltage coming out of the control board, so there are two choices: either the logic isn't requesting voltage (probably requiring replacement) or the output stage is broken, a transistor or relay most likely. I follow the traces back from the motor output to the relay. I figure out which traces control the relay, then I plug everything back in and hit start on the dishwasher, while I probe the signals. When it gets to the proper stage, 12V appears on the coil of the relay, but nothing on its output. Woohoo! Just a bad relay. Digikey even has a part. I add it to my Digikey parts list and can sleep, knowing just what needs to be done. (I could have used a spare of a different sort, but I was tired enough to sleep by that point).

But now that I've learned how all the clever little mechanisms work, it seemed a shame to hide them back under the sheet steel. So I resolved to cut out the side and add a window. I finally have.