Model Number: 795.79304.901
Brand: Sears Kenmore
Age: 6-10 years

My refrigerator's evaporator fan and interior lights are not working in normal operation. As far as I know, everything else works.

The passageway between the freezer and refrigerator froze up over time, so when I noticed that the refrigerator was too warm, I removed all food and defrosted the whole thing. After plugging it back in, the interior lights worked again. But after I checked back after a few hours, the refrigerator was still warm. I researched this issue, and discovered that the evaporator fan was not running. Also, the interior lights stopped working again after the freezer cooled down.

During my research, I found this Service Manual for a nearly identical model: Mine just doesn't have the door-mounted water dispenser.
On page 28, it talks about Test Mode, which is activated using a button on the mainboard. I tried this out, and while test mode 1 was running, the switches for the lights and the lights started working again, and the evaporator fan spun up, just like they were supposed to, and to my great surprise.

So at least I now know that my fan works, and so do the switches and the light bulbs, and the wiring is intact. Again, as far as I know, everything else works normally. There was ice buildup on the coils, but not that much, so maybe it could be explained by the lack of airflow? This assumption is based on what I've read about ice buildup on freezer goods because of a lack of airflow.

I've heard that the issue might be the defrost thermister or the refrigerator thermister, but I don't know how to check them or replace them. If someone knows more about them, that's really what I need at the moment. How do I check thermisters to see if they work? How would I need to replace them? How would a faulty one explain my symptoms, where both the fan and the lights don't turn on?

I do have a cheap multimeter (it can test for ohmage but not continuity) and a thermometer.

Thanks for any and all help.