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FIXED MDB4949SHZ0 Maytag Dishwasher - F9 TRIAC Fuse - drain pump running continually

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jhanson123

Premium Member
Joined
Jan 10, 2021
Messages
2
Location
MN
Model Number
MSD4949SHZ0
Brand
Maytag
Age
1-5 years
A couple weeks ago, when running our 2 year old Maytag dishwasher, I noticed an burning electrical smell. I traced it to the dishwasher. The drain pump was running continually. I took the sump apart internally and discovered lot's of debris in the drain catch. I cleaned it out. The dishwasher ran normally for a couple weeks. A week ago, it failed during a wash cycle, and stopped. It had water in it, but the pump was not kicking on. I figured the drain pump crapped out. I removed the original, and although it felt fine to me, I bought a good used replacement anyway. That didn't solve the problem. A DVM check showed low voltage at the pump. All lights work, I hear a relay click, but measure low voltage (~20volts) at the pump terminals. I figured maybe it needed water to work properly. I put it back together and tried a cycle. The drain pump still would not kick on when the cancel\drain was engaged. I suspected my control board had failed. Of course, finding a replacement is very difficult right now. I ordered a used one off ebay. Same result, and now it doesn't fill either. I can swap between the two boards and there's zero difference. I found the service manual for the unit, and have run through some diagnostics. My ohm checks of the drain, latch, and fill loop all check out. The stored codes are 6-4 and 8-2. Both point to a potential F9 Triac fuse issue. I tried measuring the impedance on both boards, and I get the same result, about 860 ohms. I'm not sure if I'm measuring it correctly though.

There's no burned or frayed wires upon inspection. I run through the diag cycle and it clicks through, and the wash motor runs and it heats because I can smell it, but it eventually fails and errors out (same codes). How does one properly check the F9 fuse (the service manaual is not 100% clear) and can you check the pilot relay? I fear simply trying another control board in case I'm frying them with a bad connection or bad device causing the issue.

Need help in Minnesota! Thanks!
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
117,285
Location
McMullen Valley, Arizona
The problem is the control board. Buying parts on ebay is not a good idea, there is no quality control there.

Here's the control board for your model you can order: W11225084 Cntrl-Elec

How does one properly check the F9 fuse (the service manual is not 100% clear) and can you check the pilot relay?
You are correct, it's very vague on telling you how. I don't know either.

All I know is if your not getting proper voltage to the drain pump, then the control board is the problem.

Jake
 

jhanson123

Premium Member
Joined
Jan 10, 2021
Messages
2
Location
MN
I replaced the board with a new one I found locally. This resolved my issue. I'm chaulking it up to the other two having failed F9 TRIAC fuses. Interestingly, when checking all three, they ohmed out the same. I must not have been checking the F9 fuse correctly, because a good one is supposed to have less than 3 ohms of impedance and I was getting around 870 ohms. Throughout the process I've learned more about that dishwasher than I care to. I know now you can test your inlet valve and drain pump by simply applying 120v to them. They're very simply machines, but can be expensive to fix. At least it was repairable, so many things are not these days.
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
117,285
Location
McMullen Valley, Arizona
Yes, you are correct, very easy to diagnose by just the basic 120 volts going to those parts.:)

Glad the new control board fixed it.(y)

Thanks for the update!

Jake
 
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