We have a Kenmore Elite S/S refrigerator (model 106.53293201) that is frustrating our ability to diagnose the problem.

We have two thermometers running in the refrigerator side (one electronic with a remote sensor and one mechanical).

About a week ago, the temperatures in the refrigerator side started to climb to 50 - 60 F. Freezer temps in the -10 to -15 F range. The air diffuser doors were closed and we went through the diagnostic steps for the system. Thermistors showed as pass under the diagnostic, 120V at air diffuser with no door movement. With the diffuser removed, temperatures began to drop closer to the 30's. Cut the doors out of the diffuser until the replacement arrived.

Replaced the air diffuser. Temperature went low and stayed low - down into the upper 20's (28 - 29). Air diffuser doors remained open, although when running the diagnostic, door movement can be seen. So assumedly, the replacement air diffuser is working correctly. Altered the refrigerator temp control settings, minimal change.

Removed back panel of freezer, checked coils. Coils did not have ice, although the compressor seemed to run a lot.

Unplugged diffuser, removed refrigerator thermistor and tested resistance with sensor and reference thermometer in an ice water bath. Thermistor resistances close to published specs at multiple points. Is it within 5%? Tough to say since the water bath temp is variable and it's unknown how accurate the reference temps are. Reconnected diffuser and thermistor.

Now the temp seems high on the refrigerator side (40 -45 F). Air temp from the diffuser ranges from -5 to 0 F, which would suggest the evaporator fan is fine.

What should I check now? It's gone from one extreme (too warm) to the other (too cold) and back to the first (too warm).

I don't think it's the thermistors since the temps have gone both directions and a failure would most likely be only in one direction (too high or too low).

Any suggestions?