Kenmore 51789 - Trying to Troubleshoot Defrost Problem

[webenji]

Fridge: 1.5 year old Side-by-Side Kenmore 51789 (seems to be a Whirlpool model?)

Service Sheet: W10670778 A

Over the last few 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.

[Budget Appliance Repair]

Just putting ice on the defrost thermostat/bi-metal won't be enough to make it close even if is OK.

You would need to use freeze spray or get the freezer down to under 20 degrees to get it to close - the usually closing temp on that defrost bi-metal would be some where around 15 to 20 degrees.

After defrosting and letting it run for 3 days or so and started to see the frost at the bottom of the freezer at the back panel, did you pull the evaporator cover off again to inspect the frost pattern on the evaporator coil?

If you don't have a good white frost coating over the complete evaporator and it is only iced up at the bottom that would most likely indicate a sealed system problem - The Freon/R134A coolant comes into the evaporator thru the small capillary tub and the first pass of the evaporator starts at the bottom and works it's way back up.   If it is low on coolant it will only freeze the lower portion of the evaporator coil and not get any cooling at the top of the coil so never close the defrost thermostat thus never actually turning the defrost heater on in defrost cycles and eventually the frost clogged coils on the lower portion of the evaporator stops air flow going to the refrigerator section and the refrigerator starts warming up.

Yes, the bi-metal/defrost t-stat being too warm/open will prevent the forced defrost from working also.

EDITED TO ADD:  The model number  you gave is incomplete - that is the Sears stock#.  Any time you are looking for parts or help on a Kenmore appliance you need the complete model number off the model/serial# tag.

Sears model numbers always start with 3 numbers then a DOT then 7 or 8 more numbers

Yours is built by Whirlpool so your model number is 106.5178941? I was able to find that by knowing it was made by Whirlpool so it starts with 106. and with your stock number doing a Sears lookup only shows 4 models that start with 106.51789 then next 2 number of them all are 41.  The last number is 0,  2, 3 or 4.

Edited April 3, 2020 by Budget Appliance Repair