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FIXED GE Side by Side Fridge Coils Icing Up Freezer Fine ZFSB25DXCSS

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floatingice

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Messages
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Location
San Mateo
Model Number
ZFSB25DXCSS
Brand
GE
Age
1-5 years
I have a GE side by side, set to 37 FF /0 Freezer.

Fridge is about 5 years old.

I'm finding the fridge coils are icing up after a few days.
The freezer is fine, I disassembled it to check for ice, and it appeared to have no ice.
I checked the heater for resistance and it had the right Ohm reading.
Freezer occasionally seems to run a little on the cooler side (shows up at -1,-2 or -3F) when set to 0.

There is no defrost assembly on the fridge, only some coils.
These coils work fine for about 7-10 days and then are iced up and fridge temps begin to rise.

I purchased some thermistors and heat shrink to replace those. That was going to be my next attempt to fix.

The door gasket does not appear to have leaks.

Does anyone have any other ideas?

Tonight, I'm going to attempt these ideas:

Other questions: which direction should the fan be blowing on the coil assembly? Should I be seeing hot air being pushed down over the coils, or should it be cold air pulled up from the coils. I'm worried I flipped it when I took it apart last.
 
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floatingice

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I replaced the thermistor in the fridge on the coils.

Since I bought a few new thermistors, I decided to test them, as well as the old one. Odd results.

Ice water test:
Old: 18.5 kOhm
New: 14.2 kOhm
Meat thermometer says 35.2F

Room temp:
Old:8.88 kOhm
New: 6.82 kOhm
Instant read stabilizes about 66F

The older thermistor is different than the new part with a 90 degree bend rubber gasket device to seat it properly into the block with the coils.

This to me says that the old thermistor may be bad, but is showing values that are "colder" than reality. I wouldn't have expected that to cause icing though, if anything I'd expect that to cause the fridge to not be cool enough. I ordered a laser thermometer to take some readings to see if maybe the digital readout thermistor is bad as well.

I've got the fridge back up and running. Hopefully no spoilage, but it did take me longer than expected to fix things. I ice packed the milk, and bottom meat drawer, so hopefully fine.

I'm going to run it for awhile and hopefully it can cool itself off by morning. Temperature hasn't come down much in the first 20 minutes of operation. Hope I didn't mess things up!
 

Jake

Appliance Tech - Admin
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Messages
125,702
Location
McMullen Valley, Arizona
Make sure that fan is running for the Fresh Food Evaporator Coil.

Here's the custom cool fan(refrigerator Fresh Food side) for your model:
WR17X12490 Cover Evap Asm Ff


If it is running, then you do have a thermistor that is clipped on the top of the Fresh Food Evaporator Coil, ohm test that thermistor in the glass of ice water WAITING at least 5 minutes before ohm testing it. It should read about 16.3K ohms +/- 5% in a cup of ice water waiting at least 5 minutes before ohm testing it.

Here's the thermistor for your model:
WR55X10025


Jake
 

floatingice

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Location
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Yes, I checked once disassembled. It is running when I close the door or press the door close switch.
I also checked when re-assembled by putting a plastic bag over the intake and verifying it is creating some degree of suction.

I believe with this fridge it should be blowing cold air upwards into the cooling tower, which it appears to be doing.

Really hoping the thermistor is the problem, but I won't find out for another 5-10 days if it is able to keep the ice off. Logically it doesn't make sense to me why the fridge thinking the coil are colder than they actually are would help with the it icing up. I believe now it's going to be running more, not less, based on the reading I got off the thermistors. I could be wrong though, maybe previously it wasn't running often enough and therefore when it did it would crank itself on for too long. I wish these things just had a diagnostic port you could hook up to a computer.
 

floatingice

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Messages
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Location
San Mateo
I put some cups of water in the fridge to measure the temperature. With an instant read thermometer, they're reading at 41.1F on the top shelf of the fridge, at thermal equilibrium after a night in the fridge. The fridge itself is claiming to be 36F. It seems like perhaps the thermistor that measures the fridge temperature itself might be bad as well. Anyone have any thoughts on that?

Or is 36 at the thermistor correct, and it's just a thermal gradient top to bottom which is normal?
 

Jake

Appliance Tech - Admin
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Is the compressor and fans running non-stop when it only gets to 41.1 F degrees?

Do the refrigerator evaporator coil have a even frost pattern on it from TOP to BOTTOM?

Jake
 

floatingice

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Location
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Thanks for being so helpful Jake!

a) I don't think the compressor fans are running non-stop. Will the fridge be completely silent when they're off?

b) Not sure about the frost pattern. Because of the design of the fridge, when it's frosted up you can't remove the casing because it freezes the styrofoam insulation to the coils themselves. You have to fully defrost it before you can get the casing open. Visually I can only see the bottom of the coils. It's possible the tops have already frosted up and blocked air flow to the rest of the fridge.

Repair note:
I replaced the thermistor on the coils of the fridge, but not the one in the side grill of the fridge (which I believe is used to take the reading shown on the digital reading. Could it be that this thermistor is bad as well? It seems likely given this is the control for the fridge digital output, but I'm not excited to replace it as it seems like I may rip the seal and I don't have that part on hand.

Note that the fridge is claiming to be at 36F, but the two cups of water I left in the fridge came in at in between 39 and 40.
 

floatingice

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Messages
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Location
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Checked the bottoms of the coils visible through the air intake grill. They are exhibiting frost, showing early signs of problems perhaps? The cheap etekcity laser thermometer says the coils are about 20F. I lowered the fridge temp to 35 so the fridge may just be trying to adjust internal temp.

Not sure if that will melt away throughout the day. I don't know if this indicates they will be frosted up by this weekend, but I suspect this is the case.

From a repair perspective, what would a professional do next?
 
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Jake

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a) I don't think the compressor fans are running non-stop. Will the fridge be completely silent when they're off?
Yes.

Checked the bottoms of the coils visible through the air intake grill. They are exhibiting frost, showing early signs of problems perhaps? The cheap etekcity laser thermometer says the coils are about 20F. I lowered the fridge temp to 35 so the fridge may just be trying to adjust internal temp.

20 F is too warm, should be 0 F.

From a repair perspective, what would a professional do next?
Check the frost pattern of the refrigerator evaporator coil.

Jake
 

floatingice

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Thanks for the suggestions.
a) okay, I'll try to see if they turn off. It doesn't seem like it's going full blast but it's definitely running most of the time. Online searches says it should be running about 90% of the time so not to worry. Should I measure compressor surface temp? What the diagnostic process here?

b) I don't really trust this etekcity infrared thermometer. Do you have a preferred infrared thermometer? It claims +/- 2% or 2C which is 3.6F on either side.
I ordered 2 rubbermaid analog thermometers just to put in the fridge to see how the air temps look, because I just don't trust any of these thermometers and these ones claim NSF ceritified.

EDIT: I remeasured the coils while operating, they are at 0 deg. It's hard to get the laser to aim through the grill, so the 20F is the outside of the casing, and the 0F is when I hit the coils properly. So these appear fine. They are lightly frosted at the moment. Visible coils, and metal spikey flakes, but covered in a light coating of frost, not yet a block of ice as happens in failure mode.

c) Any suggestions on how to examine this frost pattern? I can always take the thing apart, run it with the housing off by holding the door switch closed. Are you talking about the accumulated frost pattern? Given that it'll fully ice up in 1 week, I can inspect it on day 3 and likely still get the housing off. What should I look for and what is the diagnosis?

Inside the assembly is an insulating layer of foam. That foam is a little bit waterlogged from the ice ups. You can tell because it's heavy on the side that had ice build up. Even when running a hair dryer on it, I can't really dry it out fully. I think it would need to sit out for a few days. I haven't tried running the fridge without the foam, because it's what holds the evaporator fan and obviously the fridge wouldn't function well without it.
 
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Jake

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Look at the very bottom photo below:

Frost Patterns.jpg
 

floatingice

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Messages
9
Location
San Mateo
I think we can mark this off as successfully fixed. Replace the WR55X10025 part that is mounted behind the coils. It requires basic soldering skills and some marine heat shrink to function in a somewhat rugged environment. You have to pull fairly hard to get the old sensor out of the metal mounting, and it helps to have a mirror to see what you're doing.

I did not replace the other thermistors, but did assess the freezer coil and validated that the defrost heater was working. This was unnecessary given the nature of the defrost unit in this side by side.
 

Jake

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Excellent, glad to hear the new fresh food evaporator thermistor fixed it.(y)

Thanks for the update!

Jake
 
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