795.72053.118 Kenmore Refrigerator - Ice build up on fridge coils - odd case

[SKS123]

Model Number

795.72053.118

Brand

Sears Kenmore

Age

6-10 years

Hi--

I've been working on my parents' Kenmore Elite 795.72053.118 (actually manufactured by LG) french door fridge (purchased 2013). Last summer (2019) they noticed some odd noises and found their fridge cooling coils were completely iced over, requiring them to manually defrost. They had to do so again in July this year (2020). I was in town 2 weeks ago and began to troubleshoot. Here's what I've found:

• All 4 temperature sensors are reading correct resistances (freezer: 9.7k, freezer defrost: 35.2k, fridge: 19.6k, fridge defrost: 19.5k)--note that the freezer sensor's temp/resistance relationship is different from both defrost sensors and the fridge sensor.
• The fridge defrost heater resistance is around 80 ohms, within spec
• the "fuse-M" is reading 0 ohms.
• The defrost heater gets 110VAC for a second or two when the fridge is turned on, as well as when the fridge is in manual defrost mode (test mode button pressed 3 times, fridge display reads "33 33").
• The fridge was last manually defrosted about 72 hours ago. In the last 24 hours, the fridge defroster has been on once for somewhere between 15 and 30 minutes.
• I don't know if the fridge will automatically display error codes or if you have to enter some special mode to see the codes. regardless, I have not seen any error codes on the display.
• The gaskets seem to seal well, they are good about closing the doors, they live in a very dry climate (desert plains, 3200' elevation), and I don't think they excessively put steamy food unsealed food in the fridge.
• There was no issue for the first 6 years of ownership.
• The fridge fan works fine

Here's an image of the fridge coils from this summer, 1 year since the previous manual defrost. This kinda looks like a sealed system problem, maybe (though note that the lower coils, though frost-free, are encased in ice)?

Here's another image of the coils from earlier this week, about 2 weeks since the previous manual defrost. But here, the frost seems a bit more uniform?

You can check out the fridge's service manual here, if that helps. I have no hair left on my head, but if I did, I would have torn it all out by now trying to figure out what is wrong.

Do any of you kind folks have any suggestions, diagnoses, questions, anything to help?

Thank you so much!
Sandheep

 

[Jake]

Hi,

What we do is a process of elimination when the defrost cycle does not work. So since the defrost heater ohms tests good, then ohm test the defrost sensor.

Your defrost sensor should ohm at 30K at 32 degrees.

Here's the defrost sensor controller for your model:
6615JB2005R Controller Assembly


If your defrost sensor ohm tests good, then the only part left that controls the defrost cycle is the main PCB board.

Here's the main PCB control board for your model:
Pcb Assembly,main


Jake

 

[SKS123]

Jake--

Thanks for the response. I didn't mention that I had already changed out the defrost sensor (but later confirmed that both the old and new sensors are reading resistances commensurate with the respective temperature readings). I have a replacement main PCB on hand, but don't want to install it (and lose return privileges) if that's not the actual problem.

If the board is turning on the defrost for 15-30 minutes every 24 hours or so, then it should be working fine, right? For a fridge that was manually defrosted 96 hours ago, how often should the main PCB activate the defrost cycle?

Thanks!
Sandheep

 

[Jake]

If the board is turning on the defrost for 15-30 minutes every 24 hours or so, then it should be working fine, right?

Yes, correct.

For a fridge that was manually defrosted 96 hours ago, how often should the main PCB activate the defrost cycle?

I don't know, this model likely uses a adaptive defrost circuit, so it depends on the compressor run time.

But what I'm saying is very simple, process of elimination--->If defrost heater, defrost sensor, defrost FUSE-M all ohm test good, then it can only be the main PCB, you see what I mean?

Jake

 

[SKS123]

Jake--

I follow your process of elimination, but I understand that other factors can cause this problem (sealed system issue, broken door gaskets, frequent opening, unsealed steamy foods, etc). Since the main board is turning on the defrost heater, then I don't see any reason to replace it. I am looking for other potential causes to this issue--I believe that I have eliminated all the usual suspects.

Thanks,
Sandheep

 

[Jake]

If the board is turning on the defrost for 15-30 minutes every 24 hours or so, then it should be working fine, right?

Oh ok, I misunderstood. I thought you meant it used to do that before. So if the defrost heater is coming on, then the main PCB is fine.

I don't know what is causing this problem then, you do have the cover back in place over the evaporator coil correct? That must be in place for it to defrost properly at all times. Lots leave it off to check the evaporator coil and you can't do that.

Jake

 

[SKS123]

Thanks for the response. As far as I can tell, the cover is properly in place. I'm leaving town tomorrow, not sure when I'll be back here, hopefully my parents won't have to manually defrost this dang thing too often.

Thanks again for your help.
Sandheep

 

[Jake]

Ok Sandheep, I understand.

Hopefully another tech. or member that's seen this problem before can shed some light on it for us.

Jake