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FIXED GE Dishwasher ZDT870SSF7SS no heat, cycle takes much longer.

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deepthread

Premium Member
Joined
Jul 29, 2021
Messages
11
Location
brampton,ontario
Model Number
ZDT870SSF7SS
Brand
GE
Age
1-5 years
Hello.

My 5 year old dishwasher, a monogram, is running longer than the indicator says. eg Just ran an express cycle that should have been 45 mins but it ran for almost 11/2 hr.

Also it doesn't dry very well at all using the power dry or the Max dry. I've checked the diagnostics and there aren't any F codes showing, the fan is working, the heater gets activated according
to the test ( I can't really tell if its working) but I can hear the impeller in the circulating pump start to work. I assume its pushing out heat from the pump head.

I've checked the main board and it seems to be ok. Any thoughts on what's happening will help. Thank you.
 

Jake

Appliance Tech - Admin
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Location
McMullen Valley, Arizona
Hi, First ohm test the flood switch. A bad flood switch would make it not heat at all.

--->Ohm your flood switch resistance with a multimeter set on 20K ohms.
the resistance across pins 3 & 5 on the flood switch should be about 11K ohms at room temp, and 1,300 ohms at 175 degrees.

These 2 circled in red are pins 3 & 5:

floodswitch.jpg


Here's the flood switch for this model(Video Included in part link):
WD21X10519 Switch Flood Asm


Jake
 

Jake

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Ok, that's good.

Is there plenty of water in the tub when its washing? Lack of water would also cause the NO HEAT problem.

Also check the machine control board STATUS LED and see how many times its flashing, or if its STEADY ON or STEADY OFF.

D-GE control board status led.jpg


Jake
 

deepthread

Premium Member
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Messages
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Location
brampton,ontario
The service LED on the Controls Board blinks once every 3 secs. Ive noticed that the unit is not heating the water like it used to and doesn't dry the dishes .
Could it be the inverter board?
 

Jake

Appliance Tech - Admin
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Messages
123,965
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McMullen Valley, Arizona

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
123,965
Location
McMullen Valley, Arizona
So the STATUS LED on the machine control board underneath the dishwasher is STEADY OFF?

You will need a multimeter. First check for 120 volts at the Volts AC supply plug that connects to the machine control board. If you have 120 volts coming into the machine control board and the STATUS LED is STEADY OFF, then the machine control board is the problem.

Here's the machine control board for your model you can order:

Just remove the lower bottom access panel and you will see it.

See it on the right side of this photo below? Coming off the two yellow wire nuts, I circled it in red.:) Simply unplug that connector, then put your meter on Volts AC and put one meter probe in the white wire hole of that connector and the other meter problem in the black wire hole of that connector and see if your meter says 120 volts.

J722red.jpeg
 

Jake

Appliance Tech - Admin
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Messages
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Ok, sounds good.

Jake
 

deepthread

Premium Member
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Messages
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Location
brampton,ontario
Hi again. I’m getting about 100v so I plugged the dishwasher elsewhere and it does work. The MCB blinks once every three secs.
I did have a new plug installed for my DW and is most likely the problem. Thanks so much for the help.
 

Jake

Appliance Tech - Admin
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Messages
123,965
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Ok, sounds good!

Glad that was all it was.(y)

Jake
 
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