After checking the suggested fixes and parts on Appliance Parts Pros, I ordered the defrost thermostat and evap motor for my refrigerator, a Kitchen Aid KSSC42QTS00. Installation was very easy, simply emptying the freezer and removing the access panel in the back bottom half. Upon getting everything open, I found out that the existing evap motor was working fine, so I didn't install that part. I did install the defrost thermometer, which was a 5-minute process. I also cleared out the vent tubes from the freezer to the refrigerator side, and defrosted the evaporator coils while I was in there. This was an easy repair. It required a 1/4" socket drive to remove the access panel, and a heat gun/blow dryer to defrost the evap coils. Works like a champ, now!