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FIXED GE Top Freezer fridge, GTS22KBMBRCC - question on thermistor resistance readings & how to debug control board

vt_user

Premium Member
Joined
Aug 11, 2020
Messages
7
Location
Vermont
Model Number
GTS22KBMBRCC
Brand
GE
Age
More than 10 years
Hello All, hoping some of the expert folks might clarify a much earlier posting (GE Model PFS22SISBSS not cooling after control board replacement. Compressor and fan running.) Original here:

My freezer had been getting cold but the air to the FF section at the bottom is not cooling, at all. Several weeks ago, I cleared out the freezer and used a hair dryer to warm the back evaporator panel. That seems to have worked for awhile but now it's back to more trouble. I noticed, just in the last day, the freezer is still "cold", but now the ice trays (no ice maker) are not freezing in a reasonable amount of time (like over a day). There is also condensation on the 'ceiling' of the refrigerator section.

I followed the link in the post mentioned above. I found & followed advice for checking the defrost t-stat & heater and those seem to be okay, checking at the pin connectors, once removed from the motherboard. I then moved on to the thermistor check sections. I find the evap thermistor reading, J1-5 to J1-4, to be about 40-45K, with the freezer still cold, not the 16.6k ohms +/-5% as mentioned, however, Rick's input caught my eye. Guess I should mention I unplugged and took the readings within 20 minutes (i.e., freezer still "cold").

Would you be able to confirm or clarify the readings I should get? I see light frost on the freezer back wall cover and am ready to unplug and melt what I can, to get a few more days, before any needed parts arrive. If all the heater, thermostat, and thermistor readings are within range, does that mean I have a bad control board (replaced once already, maybe 4 years ago?)? Is there a way to conclusively indict the control board or, prove it's okay?

Thanks, sincerely, for any help & advice!!

Bewildered in Vt

P.S. Appears we have the control board, WR55X10942 / WR55X10942P, which seems to be problematic.
 
Last edited:

Jake

Appliance Tech - Admin
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Messages
113,135
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McMullen Valley, Arizona
Remove the back panel inside the freezer and take a photo of your evaporator coil and upload it here please. Is the freezer evaporator fan motor running inside the freezer?

Here's the parts diagram for your model:
Your evaporator thermistor is #605, its clipped to the very top of your evaporator coil in the freezer.

If the evaporator coil is completely caked up with massive frost build-up then you will need to determine which auto-defrost part is bad. Three parts control auto-defrost, the evaporator thermistor, the defrost heater and the motherboard.

Here's Shawn's video below, he mentions that if the evaporator thermistor is already covered in frost there is no need to put it in a cup of ice water for at least 5 minutes before ohm testing it.


Let us know what the evaporator thermistor reads.

Jake
 

vt_user

Premium Member
Joined
Aug 11, 2020
Messages
7
Location
Vermont
Jake, thank you! Sorry for the delay in responding - we had an electrical storm roll through later that evening (Tues, 8/11) & my computer took a hit. More bad luck & really "good" timing, right?!?! :rolleyes: Took yesterday to resolve that ugly situation.

Unfortunately, it's very difficult to take the back panel off, as I had broken one of the retaining clips on the evap fan shroud, that the back panel is held with, in addition to the two 1/4" bolt head screws in the top corners, the last time this occurred, so I was extra cautious and started to melt the built-up ice, and warm that clip up, before I could take the panel off and take a picture, BUT NOT before I took the measurements, as Shawn recommends in his video and website.

I can tell you there was a light coating of frost all over the back panel and a fairly thick layer (1/4"-3/8") of ice coming out both of the slots on the lower back panel, spilling out onto the floor of the freezer, extending out about 2-3 inches, around those areas. There were also indications of ice build up in the two square ducts in the back ceiling of the FF section and minimal cold air coming down to the FF section in the port in the front of the ceiling.

I was reading 40-45K ohms from the J1-5 to J1-4 pins, prior to any thawing. not the 16.6K ohms Shawn indicates, suggesting the thermistor was not coated in ice but reading the ambient temp in the freezer(?). Hard to believe, as the freezer would not freeze water in ice trays in a 24 hour period. Food was just starting to thaw out so I knew I had to take some action.

I also took a reading from the J9 center wire to the J7-pin 9 that was around 35-40 ohms (analog multi-meter, sorry). Shawn's website indicates that should mean good continuity for the heater and thermostat, I believe, in a top-freezer model.

I eventually warmed the back panel enough to ease it away from the remaining clip on the fan shroud (yup, that fan does run). I did look at the evap thermistor (realizing that don't mean diddly) and the thermostat (which didn't look 'bad', no bulges or separating casing). All original parts. There was definitely a good water flow down to the drain tray under the compressor, as I melted whatever was behind the panel. I had vacuumed the compressor area in the prior time. All appeared running (compressor fan, compressor, etc.).

It was approaching 90 degrees up here in northwest VT on Tuesday, so I didn't go further, as the "BOSS" was getting nervous about some expensive groceries thawing out in the Coleman coolers, so I buttoned it up, hoping the stop-gap would get me some time to get the right parts, as needed.

Glad to go back in as you advise. The freezer is currently operating, as I type this, making ice in trays, but not sure that's going to last. The FF section is cool, but I'm thinking I should go get an appliance thermometer to verify temps.

My confusion on what reading to expect off that evap thermistor, comes from Rick's response in the 2009 thread, that I should see ~ 40-45K ohms, https://www.applianceblog.com/mainf...compressor-and-fan-running.71366/#post-357775

Am I making any sense, Jake? What would you suggest as next steps, sir? All advice is more than appreciated!!

I suspect the control board is acting up, again, but, damn, those are getting expensive:

Thanks, Pat (bewildered in VT)
 

Jake

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but I'm thinking I should go get an appliance thermometer to verify temps.
Yes, most definitely. I always have one inside of mine at all times. Get the liquid or digital type. Walmart, Target sell them.

Yes Rick is absolutely correct. Here's the GE thermistor/temperature chart below.

(click to enlarge)
011 GE Thermistor Chart.jpeg

I'm not sure why this happening, but keep your eye on it, it might be a intermittent problem. But if it frosts back up again then you will need to remove the back panel from inside the freezer and take a photo of your evaporator coil and upload it here. Because when the evaporator thermistor is covered in frost your meter should read about 16.3K ohms.

Jake
 

vt_user

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Messages
7
Location
Vermont
Hello Jake & everyone!!

Well, it didn't take too long to get back to where we were, plus some possible new symptoms, or just some that I may have overlooked on the prior occurrence.
Freezer is more or less cold but not freezing ice trays again in less than 24 hrs. FF section not cold. Honestly, it didn't sound like the evap fan was running in the last day but the compressor & compressor fan ran forever.

Before defrosting manually, I again took a reading for continuity on the defrost hi-limit thermostat and the defrost heater, which showed 45-50 ohms. I also repeated the resistance check on the Evap thermistor and saw around the 16K ohm mark (unlike before, where I got the 40-45K ohms).

Here's some pics, before defrosting, as you advised. You can see the ice just below the right and left side of the back panel, on the floor of the freezer. Apologies for not catching a picture of the next point but there was what looked like a frost plug (like shaved ice, not solid), right in the cold air feed behind the "tower air fz asm", as here: WR17X11846 Tower Air Fz Asm from the diagram for the freezer here:

It was a good inch or more high and completely filled that port going into the duct.

I then carefully disassembled & pulled the back wall off, and took a snapshot of the coils. I was surprised they weren't covered, however, you can see the ice at the floor bottom, leading to the drain. This next symptom is the part I didn't see the time before: both openings, just under what they call the "Evap Eps Block, 270 & 271 in the AppliancePartsPros diagram, to the right & left of the evap coils, were pretty much plugged with solid ice, the left side about 75% or more, the right totally blocked. You can also see some ice on the styrofoam fronts but hard to catch on the cell-phone camera (sorry).

I took some more pictures and then proceeded to defrost, via hair dryer, hoping to get the cold going again, before we lost food to spoilage.

Before buttoning it back up, I plugged the unit back into the A/C outlet and watched the evap fan run with no trouble, very quiet, but no apparent issue. I tried to get a pic of the thermostat but it's tucked pretty tight behind the coils, so I did the best I could. I also attached a couple pics of the main control board, trying to show no bulging capacitors, no burned up resistors, no indicators of trouble.

Jake & crew, I'm stumped. I suspect a bad, or going-bad, motherboard but appreciate your help and advice before spending that kind of funds. It is sincerely appreciated.

Thank you!!

Pat
0823201225-00.jpg0823201226-00.jpg0823201304-00.jpg0823201306-01.jpg0823201348-00.jpg0823201355-00.jpg0823201356-00.jpgbehind tower air fs asm.jpg0823201303-00.jpg
 

vt_user

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Messages
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Location
Vermont
and, maybe I should add, with the age of this refrigerator, if it's even worthwhile trying to repair? Should I just break down and buy new?

Thanks!!!
 

vt_user

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Messages
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Location
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Update: it sure doesn't seem like the evap fan is going very strong at all. Minimal to no cool air coming down to FF section. Compressor & compressor fan running fine (so far ;) )

Thanks!
 

Jake

Appliance Tech - Admin
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Messages
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Yes, since your evaporator thermistor ohm tests good and your defrost heater ohm tests good, then it is a bad motherboard. You will also need to replace the evaporator fan motor too.

Here's the motherboard for your model:
Main Control Board WR55X10942P


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


Jake
 

vt_user

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Joined
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Messages
7
Location
Vermont
Ah, Jake, thank you again!! I was afraid you were going to say that! ;)

Appreciate the confirmation and information on both the board & evap motor!!

Will let the forum know how it goes, once the parts are installed.

Thanks!! :encouragement:
 

Jake

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Yes, on these GE models its always best to replace both, I have seen lots of faulty evaporator motors take out the motherboard way too many times.

They have upgraded that evaporator fan motor to fix it from taking out the motherboard anymore henceforth.:)

Yes, keep us posted.

Jake
 

vt_user

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Messages
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Location
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Well, Jake & crew, it's been just shy of a full week. The last part (evap fan motor) came in about 3pm last Saturday (FedEx was a might slow).

Defrosted (iced up same way, as described earlier), dismantled the back panel, and replaced both parts (motherboard and evap fan motor). Cleaned the grounding screw that attached to the evap fan motor wires, and put it all back together. So far, so good.

Runs well with it on the "5" setting (dials on this older model), for both freezer and FF section, and all appears to be working well (no jinx, ya hear). Fingers crossed that I can get a few more years out of the unit. I did go get a couple thermometers and will put those in today, to help keep an eye on the performance.

Thanks for the advice and counsel!! Call this one FIXED!! Whoweee!
 

Jake

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Excellent Pat, glad to hear the new motherboard and evaporator fan motor fixed it.(y)

Thanks for the update!

Jake
 
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