Kenmore 51789 Fridge - Trying to Troubleshoot Defrost Problem

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
5. N/A
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.