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ZIS_480DHB GE Monogram Refrigerator Strange No-Cool Issue

aratari2600

Premium Member
Joined
Sep 2, 2022
Messages
4
Location
Michigan, USA
Model Number
ZISB480DHB
Brand
GE
Age
6-10 years
Hello everyone. First up - this form is fantastic and thank you to all of you that help us DIY'ers out here.

I've been reading several prior threads and I have found some great information in them but I wanted to post my own issue since it sounded similar to GE Refrigerator ZISS420DHASS Not Cooling-Failed Control/Sensor test but I believe my evap motor and input voltage is fine, so I don't think its that...

Brief Storyline:
Ever since I have had this fridge, it's been a headache. During the first no-cool event about 2 years after I had the unit, it was still under an extended purchased warranty and the tech just ordered random parts w/out actually doing any diagnostics on the board itself or even putting the fridge into diagnostic mode. Whenever a subsequent no-cool event occurred, the techs would just order parts which would infuriate me because nobody has gotten to the root issue here. So over the course of the year(s), I have gotten 3 new motherboards, a new evaporator fan/motor, and 2 stat cutoffs all from GE directly.

Now in the past few years, I've become very attuned to my fridge and I know when it's going to stop cooling since the compressor and condenser fan is running but I do not hear the evaporator fan on. I have to vacate the entire freezer and fridge, fully de-thaw it and when it starts back up it runs for many months just fine. When this has happened twice over the past year, I would immediately dismantle the freezer section (boy I've become a pro now at this :) and look at the evaporator to see if it was a block of ice but it was not.

So this is where I'm at. I've been looking for diag manuals for my specific motherboard (WR55X23124) and in these forms I've found very similar ones posted from Rick in the past (I saw the comment about Rick earlier this year about his illness - I hope he is ok ..). Armed with that and a few other diag manuals that have been posted (but are not quite the same model I have), I've been able to verify voltages to the evap motor and supply to be correct (J2-3 to J2-4 was 12.5v, J2-3 to J2-8 is 13.7v). I've also put my fridge into diag mode and I've run the tests of 02, 03, 07, 15. All pass minus 07. For the 07 thermistor test, I get a P,P,F,F,F. I've been trying to determine if that means my custom cool, evap and freezer thermistors are shot or not and that could potentially be my issue here... When (it's not even a question heh) this occurs again, I want to start probing things to try to figure out why it's stuck (waiting to defrost? thermistor bad reading?).

I did just order 2 GE thermistors for my unit - since the freezer thermistor is easy to get to, I was going to try to replace just that one, run another diag test, and see if I get one of those fails to pass... It's going to be a royal PITA to get up in the freezer compartment to replace the evap thermistor so wanted to do this test first :)

If anyone has any advice or help - would love to hear it and discuss. Thanks again everyone.
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
134,013
Location
Redmond, Oregon
Yes, it does sound like either the evaporator thermistor or defrost heater is bad. You can ohm test the evaporator thermistor is a glass of ice water, waiting at least 5 minutes, then it should read about 16.3k ohms.

Here's the evaporator thermistor for your model:
WR55X10025 Temperature Sensor


Read this thread on how to access it:

Also this one:

Here's the defrost heater for your model:

Jake
 

aratari2600

Premium Member
Joined
Sep 2, 2022
Messages
4
Location
Michigan, USA
Thanks Jake.

I will first test out the defrost heater (as in the other threads mention how) from the main board and will report back.

If that looks good, then I will have to find a time when I can vacate the freezer and do the thermistor tests. The evaporator thermistor is so far up inside the ceiling of the freezer compartment, it's going to be challenging to even be able to hold it in a cup of ice for that long :)

Have you come across why one or many failed thermistors would cause the diag test #07 to trip 3 fails like that before? On the thermistor topic - my unit has an ambient thermistor as well. I see it's plugged into J14-1. Would you happen to know if that is being reported in the diag 07 test instead of the custom cool by chance? Or is it all pretty much standard across the models.

Thanks again - Tom
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
134,013
Location
Redmond, Oregon
Have you come across why one or many failed thermistors would cause the diag test #07 to trip 3 fails like that before?
Nope, but I have not worked on this particular model, also I don't rely solely on the diagnostics, I always TRUST my multimeter more, per say, to find the failed part.:)

Jake
 

aratari2600

Premium Member
Joined
Sep 2, 2022
Messages
4
Location
Michigan, USA
Thanks @Jake . I wish I would have had you come help me diagnose my fridge over the years.

So... the fridge is currently in it's 'bad' state. Evap fan is not on and fridge is warming up.

I got out the multimeter and started to probe around. Here's what I got:

Defrost Circuit Resistance : 38.6 Ohms (higher than 20 than in the other 'expected' range in the other posts.. OK?)

Fan Output Voltages:
Supply: 13.6v constant
Condenser: 12.9v constant
Evaporator: It's not constant - jumping between 11v to 13.6

Thermistors:
FF1 & FF2 : 10K each (makes sense fridge digital panel says 49)
FZ: 29.5K
FZ Evap: 55K

Thinking motherboard and should I also replace evap motor since the voltage is pulsing?

Tom
 

aratari2600

Premium Member
Joined
Sep 2, 2022
Messages
4
Location
Michigan, USA
Just wanted to post another update - I still had my old motherboard from last year so I thought why the heck not and try pop'ing that back in.

After swapping it and turning the power back on, it ran through a defrost cycle immediately and eventually the evap motor came back on - reads 12.7v constant...

Could this be the power supply PCB? Is there even a way to test this?
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
134,013
Location
Redmond, Oregon
Sounds like a bad control board to me.

Here's the main control board(motherboard) for your model:

Yes, the evaporator fan motor is best to replace too when you replace the main control board.

Here's the evaporator fan motor for your model:
Evaporator Fan Motor WR60X10185


Could this be the power supply PCB? Is there even a way to test this?
Not that I'm aware of.

Here's the power supply PCB for your model:

Jake
 
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