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FIXED 106.51789413 Kenmore Refrigerator - Trying to Troubleshoot Defrost Problem

webenji

Premium Member
Joined
Apr 2, 2020
Messages
4
Location
United States
Model Number
106.51789413
Brand
Sears Kenmore
Age
1-5 years
Fridge: 1.5 year old Side-by-Side Kenmore 51789 (seems to be a Whirlpool model?)

Service Sheet: W10670778 A

Over the last couple of days, I’ve noticed my fridge and freezer were slowly getting less and less cold, with the fridge seemingly doing worst at keeping cold. Looking at the freezer, I discovered some frost towards the bottom, right around the vents. I decided to (manually) defrost the fridge by turning it off (from the front-panel, leaving it plugged in).

As the fridge was defrosting, I looked for some information online, which all indicate that it’s probably due to the control broad, defrost thermostat, or heater. I opened up the back panel on the freezer to find that the bottom portion (directly behind the vents) was very frozen/frosted, but the top (where the defrost thermostat is) was essentially free of frost. I ran the diagnostic tests from the service sheet (see results below), with the bi-metal test returning “bimetal open”. Since the fridge was already at room temperature, I believe that test to be normal (is that correct? the bimetal is open when the freezer is at room temperature, right?). Since there was still a lot of frost, I tried to initiate “Forced Defrost” and couldn’t get it to work (does the open bimetal prevent the “Forced Defrost” mode?).

After a day/night of defrosting manually, I turned the fridge back on and it seems to be working fine/better, although I’m already seeing a little bit of frost/white on the coils (they looked dry when I turned it back on, but maybe they were not). After being back on for about 3 days (and everything being seemingly fine), I ran the diagnostic tests again and got the exact same results (see below), with the bimetal test still showing open. Although I believe this indicates a bad Defrost Thermostat (is that correct?), I’m not sure that’s the case. I wanted to try to bypass the Defrost Thermostat but it’s plugged directly into the outlet, so that would require cutting the wires to do so. I also tried to make the Defrost Thermostat cold by putting frost/ice directly on/around it to make it colder but still got the open result in the test diagnostic.

Am I correct that this indicates a bad Defrost Thermostat? Is there a difference between a "Defrost Thermostat" and "bimetal"? Is there a good/foolproof way of testing it? What are my next steps? I’m trying to narrow down the problem as much as possible before committing to cutting wires and/or buying new parts….

As an additional question, I was unsure how to get the “Forced Defrost” to work (step #38 in service sheet) because it says the “command shall be sent at the exit of Service Mode”. Does that mean that I have to select the Defrost Mode (Short or Long) and exit straightaway? or do I need to go back to the step menu before exiting?

Diagnostic Tests Results (same results when freezer was at room temperature and when cold):
1) FC Thermistor: O1=Pass
2) RC Thermistor: O1=Pass
3) Evaporator fan motor and Air baffle motor: displays O2 (baffle is closed) and then switches to O1 (baffle is open)
4) Compressor/Condenser Fan Motor: O1=ON
6) Defrost heater/Bi-metal: O2 = Bimetal Open
7) Defrost Mode: I set it to O1=ADC ON as indicated in the service sheet. How would you go about setting it to O2 = Basic Mode (8 hour timer) since it says “The Defrost Mode must be set to ADC ON before exiting the Service Diagnostic Mode”?

Any help would be greatly appreciated.

Added complete model number
 
Last edited by a moderator:

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
111,962
Location
McMullen Valley, Arizona
Read the model from the tag inside the machine. The model number tag is located inside the refrigerator section on the upper walls or ceiling.

Here's the results I get:
106.51789410
106.51789412
106.51789413
106.51789414

Jake
 

Jake

Appliance Tech - Admin
Staff member
Joined
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Messages
111,962
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Thanks,

Yes, the defrost thermostat has to be frosty when you run that test, or the bi-metal(defrost thermostat) will ALWAYS say OPEN.:)

To manually ohm test it, you will need a multimeter.

Here's the multimeter I use:
Multimeter DM10T


You can get a multimeter at any hardware store too.

You will need to ohm test the defrost thermostat for continuity while its still covered in frost, and ohm test the defrost heater too. Unplug your refrigerator first!

If the defrost thermostat is not frosty, you can still test it in a cup of ice water, watch the video below. You'd need to keep the defrost thermostat in the cup of ice water at least 5 minutes before ohm testing it.

Watch this video to ohm test your defrost thermostat if yours is NOT frosty:

Here's your (bi-metal)defrost thermostat for your model:
WPW10225581 Defrost Thermostat


7--->Defrost Mode: I set it to O1=ADC ON

Just leave it set to ADC ON and don't change it.

Take a photo of your evaporator coil and upload it, we need to see the frost pattern of it.

Let us know what you find.

Jake
 

webenji

Premium Member
Joined
Apr 2, 2020
Messages
4
Location
United States
Hi Jake,

Thank you for your response and sorry for my late reply. I was waiting for the problem to manifest itself again before replying, so that I could take a picture of the frost pattern.
Anyway here are my recent findings/tests:
1) It took about 3 weeks before happening again (see attached picture). Somewhat surprisingly (to me, at least), the frost seems worst than before.
2) This time around, I cut the defrost thermostat off so that I could test it. Doing the "ice water" trick (5+ minutes), I believe it is open: at my lowest ohm setting ("RX100"), the needle (yes, I have an analog multimeter :() moves slightly to the right (almost not noticeable), but nowhere close to the 0 Ohm it should be at.
3) I closed the defrost thermostat connection manually (and temporarily) by connecting defrost thermostat wires together and ran diagnostic test #6 (Defrost heater/Bi-metal), which now showed, as expected, "O1 = Bimetal Closed".
4) With the aforementioned manually-closed thermostat connection, I was able to start/launch the Forced Defrost mode from the diagnostic tool (the heater turned bright red and the freezer defrosted in ~30 minutes). My guess is that it means the heater is fine.
5) I have ordered a new defrost thermostat that I should receive this week-end.

I'm fairly convinced that the defrost thermostat is the issue (although I guess it could also, technically, be an issue with the timer/board), but I'm happy to get any feedback/comments you may have.
Thanks again,
Ben
 

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Jake

Appliance Tech - Admin
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You nailed it Ben! The defrost thermostat is the problem.:)

The new defrost thermostat will fix it!

Jake
 

webenji

Premium Member
Joined
Apr 2, 2020
Messages
4
Location
United States
Thanks for all the help Jake.
I'll repair the fridge (hopefully this week-end) and will post back once I'm confident the fridge is working again. Speaking of which, is there anyway to tell whether the fridge is working again after installing a new defrost thermostat? Is the only way to tell to wait 1+ month to see if it breaks again? or listening if I hear water dripping from being defrosted?
 

Jake

Appliance Tech - Admin
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Messages
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Yes, with the new defrost thermostat once its covered in frost, then run diagnostic test #6 (Defrost heater/Bi-metal), which SHOULD NOW show as expected--->"O1 = Bimetal Closed".

Jake
 
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