Fridge WRS321SDHZ08 "Adaptive Defrost Controller" function not working, anyone understands its inner workings?

[huron]

This fridge was bought from a tent sale clearance new with some cosmetic damages.  It was sold as is with no warranty.

The refrigerator operated fine for a month (used infrequently) and then I noticed that there was ice buildup on the evaporator coil.  The defrost cycle was not coming on.  Got into the service mode and I was able to manually activate the defrost cycle and saw the heater come on.  This tells me the defrost activation function, relay and wiring were OK.  The service sheet said the defrost heater should be about 600W, that translates to roughly 24 ohms.  I measured my heater and found it to be 120 ohms (about 120W) and thus concluded that the heater was not getting hot enough to melt the ice during the allotted defrost cycle time.  I bought a new defrost heater and installed it.  Several weeks later, I found ice buildup again so the new defrost heater did not fix the problem.

I verified again that the service mode activates the defrost heater and it does.  I verified that the defrost thermistor (2.7K@room) and it's resistance matches its sensed temperature when cold.  If you see the attached schematic, there are no defrost timer or defrost thermostat, it's all microprocessor controlled.  Running out of ideas, I bought a new identical controller board (W11321510 ) and put it in.  Still the same problem, no defrost cycle!  I have put a data logger on the defrost heater element and it never sees any voltages at all, that is to say that the defrost heater is not shutting off prematurely.

I checked the freezer door switch in case the adaptive defrost controller is counting the number of door openings, the switch's NO/NC contacts both work.  I have run of ideas other than some wiring harness problems, even then, what wiring could be wrong?

Anyone knows in more details how the adaptive defrost controller looks for in terms of environmental conditions that it needs to see in order to trigger the defrost cycle?  BTW, the FC and RC both regulates temperature fine.

[16345Ed]

Replace the defrost control the exact logic of the board is not documented nor does it matter. 
 

You have proved it’s not initiating defrost on its own. It needs replaced. 

[Budget Appliance Repair]

18 hours ago, huron said:

I bought a new identical controller board (W11321510 ) and put it in.  Still the same problem, no defrost cycle!

@16345Ed Looks like he already tried that

I haven't looked up anything on this so don't know if there are more than one board and maybe wrong board replaced.

Edited September 22, 2022 by Budget Appliance Repair

[MrApplianceMatt]

 Junk that plastic clip and zip tie that thermistor straight to the evaporator.

Edited September 23, 2022 by MrApplianceMatt

[dondeck]

Anyone find the cause on this? I have the exact same problem on a 2022 model. Commanded the heater and it turns on. I know they have updated the ACU part number to W11566851. 

[StaggsHomeAppliance]

I'm also having a defrost issue with this model. Marcone shows the control board W11321510 to be replaced by W11566851. So, I ordered the updated part number and that's what shows on the box. However, the board inside is the older part number but with a different revision letter than what's already on the refrigerator. Any insight as to whether those revision letters mean anything? 

[StaggsHomeAppliance]

Does anyone have anything else to add on this refrigerator model with defrost problems? I've been called to check this refrigerator for the third time with the same problem....evap freezing over. All components test ok. Replaced the control board and defrost thermistor anyway. I even ziptied it directly to the suction line without the plastic clip. Door seals are in great shape and sealing correctly. 

[StaggsHomeAppliance]

@huron do you recall how you repaired this refrigerator? 

[A Plus]

Were you able to figure out?

Did you check defrost heater molex connectors? Especially the one with Green&Black harness. I had service call today for model WRS315SNHM06 with exact same issue. During the Forced defrost cycle, I noticed it was not drawing any amps, as soon I touched that green&black harness, amps started drawing.

[StaggsHomeAppliance]

19 hours ago, A Plus said:

Were you able to figure out?

In my case, I was not able to figure out what was causing the machine to freeze up or not initiate the defrost cycle. I could command defrost in the diagnostic mode and the heater would operate fine. Give it a week or so and the evap coils would be full of ice. 

[dondeck]

I’m thinking it’s a board issue I’ve had a few of these. I defrosted the refrigerator manually. Verified heater worked and discarded the plastic clip. I haven’t had a callback yet but I will eventually. 

[dondeck]

Finally got the callback. Has anyone figure out these issues yet? I may refer to factory.

[StaggsHomeAppliance]

On 8/3/2023 at 10:43 AM, dondeck said:

Finally got the callback. Has anyone figure out these issues yet? I may refer to factory.

In my case, the owner decided to scrap the machine. Nothing about it made any sense. 

[Nathaniel Peterson]

On 8/4/2023 at 6:31 PM, StaggsHomeAppliance said:

In my case, the owner decided to scrap the machine. Nothing about it made any sense. 

If this has a dispenser board then that is what's responsible for temperature regulation per Whirlpool.

[Nathaniel Peterson]

Just now, Nathaniel Peterson said:

If this has a dispenser board then that is what's responsible for temperature regulation per Whirlpool.

Also we've been finding leaks at the steel to copper lok ring connectors pressure tested at 150 PSI. Very small leak using big blue micro leak detector.

[CullenG0]

On 8/6/2023 at 4:49 PM, Nathaniel Peterson said:

If this has a dispenser board then that is what's responsible for temperature regulation per Whirlpool.

Thank you. I’m hoping it works. The pics above look exactly like what I just came from. Searched everywhere for the ADC. Assumed it was on the main board. I can’t see how the DF Element is controlled by the dispenser board from the wiring diagram. 
* - Mine, the single lead to the DF element was not connected and rusted. Virgin disassembly and they’ve had it for 1.5 years….

Edited September 20, 2023 by CullenG0