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Author Topic: GE Monogram ZISB420DRB over cooling  (Read 695 times)

Offline imzjustplayin

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GE Monogram ZISB420DRB over cooling
« on: March 05, 2019, 03:01:32 PM »

GE Monogram ZISB420DRB overcooling issues. This refrigerator has a temperature read out which displays actual temperature in addition to the preselected temperature. I have the Freezer set to 6F and the refrigerated section set to 46F, yet the refrigerated section gets down to 35F and the freezer section is at 4F. I tried a full reset and the unit has been cleaned out of its food but to no avail. I've replaced ALL of the thermisters except the one on the evap/section behind the metal shield in the freezer section (assuming there is more than on on/near the evap).


I've done tests on all 3 dampers (two for the express chill, 1 for the freezer to fresh section at top) and they all actuated properly. The EVAP fan works properly and there is nothing blocking the dampers that I can see.


I noticed that when the unit is warm like room temperature and then I turn it on, it is capable of getting its temperatures pretty close to their preset. However, after about a week or so, it eventually migrates to temperatures that are outside of its preset settings. This makes me think it's a thermister issue, perhaps with the evap thermister. I see no indication of frost buildup anywhere however, though I did not remove the rear freezer panel.


I technically could borrow a control board from another GE refrigerator which I believe uses an identical board but I'd like to do that option as last choice. I replaced this motherboard a few years ago because the condenser fan was spinning slowly, so I replaced the motherboard and the condenser fan motor and it spins normally since then.




Any other ideas? Could a defrost thermister cause this issue especially if the unit doesn't have any issues at all with frost build up on the evap coils?

Offline Bearcat

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Re: GE Monogram ZISB420DRB over cooling
« Reply #1 on: March 12, 2019, 11:07:40 PM »
Did you ever figure anything out on your refrigerator ?  What’s wrong with 35 refrigerator, and 4 freezer?

Offline imzjustplayin

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Re: GE Monogram ZISB420DRB over cooling
« Reply #2 on: March 14, 2019, 06:58:15 AM »
Well if the temperature setting is 46f (highest) for the refrigerator and its actual temperature is displaying 35f, that's a problem. When the power goes out and the temperatures are reset to factory default which I think is 43f refrigerator and 0F for the freezer, refrigerator temperature drops down to 32f. Any of these temperatures are too cold for this model because one temperature reading of 35f can effectively be less than 35f somewhere else, leading to freezing of the water tank for the water dispenser. The refrigerator should be capable of respecting the inputted temperatures is my primary concern.

Offline dab147315

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Re: GE Monogram ZISB420DRB over cooling
« Reply #3 on: March 14, 2019, 10:11:14 AM »
There is this service pointer! Take a look.

Offline imzjustplayin

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Re: GE Monogram ZISB420DRB over cooling
« Reply #4 on: March 14, 2019, 06:45:30 PM »
I believe I already have that shim installed. Other people have worked on this unit in the past. The dampers in that section do work properly when I go into the diagnostic mode.


Attached is the image I used for reference for checking the thermistor values. Though the issue is, it shows I think only two thermistors for the fresh section while I believe I had three thermistors in that section.


http://www.msaworld.com/wp-content/uploads/sites/3/2014/05/GE-Monogram-Diagnostic-Mode.pdf
Used that guide to get into the diagnostic mode.


The o
« Last Edit: March 14, 2019, 06:53:07 PM by imzjustplayin »

Offline imzjustplayin

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Re: GE Monogram ZISB420DRB over cooling
« Reply #5 on: March 16, 2019, 05:09:04 PM »
Update. So I just checked the express cool drawer and saw that the damper was partially open. I pressed the express chill button to turn it on then turn it off and the damper closed normally. Does this damper get controlled by anything else besides the express cool drawer, such as the main board which is on the top of the refrigerator? Or are these two dampers exclusively controlled by the express chill drawer. The damper didn't look frozen in place, looked more like a computer glitch of some sort,

Offline Bearcat

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Re: GE Monogram ZISB420DRB over cooling
« Reply #6 on: March 16, 2019, 07:39:29 PM »
The answer to that question and the possible solutions are listed In the first paragraph of service bulletin REF18-03.  Although, I believe the answer is actually casually mentioned at the left bottom of that bulletin as well, about replacing the damper assembly with part number WR31X10021, and the shim part number WR97X10098.  As we have found many times, the manufacturer will sometimes give us the answer in a bulletin, but it is usually buried in the list of other things to check.

Bearcat

Offline imzjustplayin

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Re: GE Monogram ZISB420DRB over cooling
« Reply #7 on: March 17, 2019, 09:11:06 PM »
which thermistor gives the displayed temp on the fresh side? or is it a calculated number by the main computer board?

Offline imzjustplayin

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Re: GE Monogram ZISB420DRB over cooling
« Reply #8 on: March 17, 2019, 11:31:50 PM »
The quick cool drawer had been set to "citrus" for some time when all of a sudden, without doing anything to the refrigerator, the quick cool fan turned on its own.  I looked inside, removed the drawer and saw the dampers were closed when this fan was running. So I cycled through the quick cool feature then back into the off position and everything turned off.

Is this quick cool fan controlled by the main ECU in anyway?

Offline Bearcat

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Offline imzjustplayin

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Re: GE Monogram ZISB420DRB over cooling
« Reply #10 on: March 18, 2019, 02:15:22 AM »
yes that helped somewhat. Sounds like it's mostly operating correctly except for that time I caught the dampers being partially opened. The QC drawer set to citrus shows a set temp of 43 but actual temperature of 41 and the fans weren't on, so I was surprised at that. Wondering if there is a temperature threshold where it will and will not actively try to bring the temperature up or if the unit is just malfunctioning. The refrigerated fresh section is set to 40f with the temp displaying 35f despite all the dampers being closed, or at least I think they are.  Made some temperature adjustments to the freezer section from 5f to 0f to see if the refrigerated section gets colder or if it's able to maintain its temperature.

Offline Bearcat

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Re: GE Monogram ZISB420DRB over cooling
« Reply #11 on: March 18, 2019, 02:42:25 AM »
You said you found the dampers partially open once.  In my opinion, I would be replacing the dampers.  To me it is like a stalled condenser fan.  You might be able to tap it, and get it to start spinning again, but I would never trust it.

Bearcat.

Offline imzjustplayin

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Re: GE Monogram ZISB420DRB over cooling
« Reply #12 on: March 18, 2019, 03:14:38 AM »
I'm just wondering if I keep the QC Drawer in the off position where there is no temperature setting at all vs. citrus, produce, meat, will it still have those dampers actuated at all by the refrigerator ECU?

If I never use the QC drawer, will those dampers still be actuated by the refrigerator ECU? The picture diagram I looked at wasn't exactly clear at which ECU I was looking at as it could have been a "mullion" ecu vs. the ECU on top of the refrigerator in the front.

 I ask this because during the diagnostic tests from the freezer/fridge top control panel, I conducted a damper test and it tested the QC dampers down below. If I turn off the QC drawer (no temp setting for citrus, produce or meat), I'd hope that those lower dampers don't get actuated at all but I don't know.