This week’s post: Dishwasher repair! Troubleshooting, resolution of the wrong issue, finding the actual issue, and some handy tips and tricks for sorting your dishwasher out. I’m talking today about a Frigidaire FFBD2411NS6B, but this should apply to an awful lot of models of diswasher - at least Frigidaire, if not others (since all the brands are basically the same thing anymore).
The Problem
My problem was simple enough: The dishwasher stopped filling reliably. Sometimes if you started it again, it would work, but that rapidly stopped working and led to a dishwasher that simply wouldn’t fill. This, of course, renders the unit rather useless - and that’s a problem for us, because we host a pretty big weekly lifegroup gathering with at least two loads of dishes coming out of it. Hand washing is an option for a little while, but… how hard can a dishwasher be, really? My first step was to replace the fill valve, which I’d been planning to do anyway since the old one was buzzing pretty badly, but that didn’t fix the issue. So, further in I went.
Dishwasher Conceptual Overview
If you’ve never thought too hard about how your dishwasher works, neither had I! It works, it washes dishes (somewhat poorly in our case), and I generally don’t go diving into things unless I’ve got a reason to fix them. Of course, now, I had a reason to fix our dishwasher. The bulk of the mechanical bits are underneath - remove the kick panel in front with a few screws, and just about everything is exposed. If you need to work on something major, the dishwasher should just slide out - it may be screwed in place up front, but “check for anything securing it and pull it out” should get you quite a bit of space to work, though you’ll want to check for tight hose lines and such - I’d have to drop the water line off ours to get it out more than a few inches.
Our dishwasher has a handful of major parts beneath: The water fill valve is in the front left, with the hose fitting on it. The motor in front is apparently the drain motor to kick water out into the sink drain. Further back, there’s the wash motor, which routes water through the various spray bars (and, at least in ours, cycles between them based on pausing briefly - something in the water direction valve responds to a lack of pressure by ratcheting to the next position). Inside, there’s a water level sensor that’s simply wired in series with the fill valve power (out of frame to the top), the heating coil, and the actuators for the soap dispenser and any “how dirty is this?” sensors. Not bad, really.
The control boards are typically up in the top of the door, by the control panel. Details on accessing them vary based on model, but for a cheap Frigidaire, here we go!
Initial Troubleshooting
My initial troubleshooting was simple enough. Pretty much everything “down below” in the dishwasher operates on 120V, via power switched from the control board. I pulled the connection off the water fill valve (I’ll suggest turning the circuit breaker off while you do this - it’s a bit easier than it looks to make contact with something live and get that 60Hz tingle), stuck my voltmeter in it, and started a cycle. A little twitch of the needle that indicated there was a faint signal to it, but certainly not the expected 120VAC between the pins. Tracing the wiring led me to the level sensor switch in front, so I tested that out - it’s literally just a little microswitch that cuts power to the fill valve if the water level gets too high. No problems there - a clean low resistance when not tripped, going to open circuit when tripped. So, I went upstairs to figure out what was going on.
I’m going to give you a hint here that would have saved me a ton of time: See all the white wires under here? They’re neutral. Neutral and ground are bonded together in any typical modern house wiring system - so if you don’t have proper voltage between hot (the pink wire into the fill switch) and neutral? Go check hot versus ground. The entire metal frame is grounded, and if I’d checked that, I would have saved myself a non-trivial amount of time and money trying to fix this problem. Also, at least on this dishwasher, not all the neutrals go the same way. Some of them go back up to the control board (the fill switch and drain pump, for instance), and other ones seem to come together beneath. I assumed (wrongly) that the main motor running dry meant the wiring was good. But I’ll get there…
Getting Inside
You can probably find a YouTube video for getting into your dishwasher, but those aren’t really working on my machines right now - something about the audio pipeline in Qubes is fouled out after my 4.2 upgrade, so videos don’t play. It’s simple enough, though: Look for screws and remove them. Here, there’s a set of six hex-headed screws around the top of the door inside, plus some Phillips head ones lower down. Unscrew the six around the top.
That allows the front control panel to flip down. The control board is under the cover - continue removing screws to access things.
But first - look down inside the door pocket. You may find something exceedingly valuable and difficult to find online: The Service Data Sheet! It’s the sheet for my specific unit, tucked neatly inside where someone can find it when troubleshooting. I’d have saved a lot of time searching online and trying to read blurry scans if I’d looked here first, but I had no idea it would be in here. I’ll get to this sheet later!
With the cover off, the control board is exposed. First impressions are that nothing is particularly out of place looking - it’s not charred, and since all the buttons and LEDs work, the controller side seems fine. A couple more screws, a few connections, and this thing comes out too.
Touring the Control Board
There’s really not a lot on here. The right hand side is the high voltage side - a bunch of 12V switched relays handling the 120VAC that flows around to power everything. The left side is the low voltage side with the microcontroller and the interface to the panel. In the center, a transformer serves to drop the voltage down. Short of frying the microcontroller, there’s nothing here that can’t be easily replaced if it goes bad - which is very welcome these days. I’m not sure what the microcontroller is, but the entire board is a Spitfire Controls SF2501-K1001, Rev A, model A03091001.
Flipping it over, there’s really nothing of note here. It’s a basic single sided appliance PCB, of the sort that is utterly trivial to trace and debug. Everything on it is through hole, which is a bit of a surprise, but it’s quite welcome - it makes parts replacement super easy.
I went around tracing the wires from my handy-dandy wiring diagram, through the connector, to the respective relays. This is what each relay controls on this board. I was a bit confused as to how the heater relay worked, because I didn’t see anything that looked like a high amperage trace in the board going to the main connector, but a bit more puzzling it out revealed that the neutral came in on the 7-pin connector to the left, the line came in with the black wire over on the right, and the heater went out as the red wire. Interesting, though not implied in the wiring diagram. Like certain other nuances of the wiring.
Anyway, if I let the unit sit, after not filling with water (despite the relay audibly clicking), the wash motor would “dry run,” and I didn’t have voltage down at the base, so… bad relay. I thought. Oh well, they’re not expensive, and I overnighted a handful from DigiKey (seriously impressed, guys - I ordered after 5PM and they did show up next day).
Replacing the Relay
Replacing the relay is dead simple with this sort of board. Get your solder slurper spring tube thing, heat up the solder, slurp it out, and then rock the relay free with a touch more heat on each leg. It’s the most straightforward repair I’ve done in a long time.
The board is well labeled and everything!
But…
And, of course, after putting everything back together, it still didn’t work. No change in behavior. So, further into troubleshooting and learning things about this dishwasher that weren’t implied in the wiring diagram.
I started by probing voltage relative to ground, as I mentioned earlier - and had a solid 120V between the hot line for the fill valve and ground. Well, that’s odd. After a bit more probing and continuity testing, I discovered that the neutral between the fill valve and the control board wasn’t really… good. There was no damage to wiring visible, so I started tracing wires a bit more and discovered that the neutral between the board and the bottom (at least, the fill valve and drain pump) went through the door switch - and was fried. Of course, just hidden enough not to be obvious until you looked there. But one of the connections was toasted, and wasn’t passing current. How the board worked at all here is actually baffling to me - I thought this was the main neutral for the board, which would mean that if it was open circuit, the board wouldn’t work at all. Anyway, I had good continuity from the board here, and nothing further down.
This switch serves to disconnect both hot and neutral to the control board when the door is opened - it’s a hard power cut to the dishwasher. It also, however, means that if it’s got problems, the dishwasher won’t work. A bad door switch is a common enough problem, though usually manifests as a simple failure to operate. Not a problem with only a few actuators and motors!
The switch is actually still good. Just fried. I have a replacement on order now (used but tests good), though they seem to be a discontinued item. Grrr. It’s only eight years old!
Cleaning up and ohming out the switch indicated that, while toasty, it still worked. And I still want a dishwasher while I’m waiting for parts. The bigger problem is that the connectors were also crunchy, and I cannot for the life of me find what these are or find a replacement for them. Fortunately, I have a lot of electrical parts laying around my office!
Fundamentally, all I need are some new (Insulated! You’ve got line and neutral right next to each other in here!) spade terminals on the ends - so I cut off the toasted insulation, re-stripped the wire, and put on a set of insulated spade terminals for all the wires. I’ll suggest that your life with this style terminal will be far easier if you slide the terminal insulator back before trying to crimp things - it’s quite a bit easier that way than going through the plastic strain relief and getting a solid crimp.
With that fixed, I was able to make the existing door switch work for now. I’ll replace it with the new switch assembly as soon as it shows up, and I should be good for another while. Or, at least, until I get around to replacing the dishwasher with something quieter. Ours is really quite loud, and I understand there are units that you can’t hear running even standing next to them, which would beat the pants off hearing the thing “gervoosh“ing throughout the house.
The Service Data Sheet
For your reference and entertainment, the Service Data Sheet - which is actually pretty good.
The troubleshooting steps for “Doesn’t fill” do, I’ll point out, include “control board” before “run down wiring issues.” In any case, I now know more than I did before!
There’s a handy little cycle test mode too, though I didn’t need to use it here.
As near as I can tell, the wiring diagram here is somewhat wrong. It shows everything coming through the door switch, and as near as I can tell, the main wash motor was perfectly happy to run with that neutral not exactly working. I’m not 100% sure how anything worked, but… check the door switch, I suppose, if you’re troubleshooting weird voltage issues.
It even includes cycle diagrams for what you should expect, by minute!
Seriously, more stuff needs datasheets like this.
Anyway. Dishwasher fixed! And more troubleshooting skills learned.
This is a companion discussion topic for the original entry at https://www.sevarg.net/2024/07/07/frigidaire-dishwasher-repair