Going back to the OP. I had a fridge/freezer unit doing the same - freezer still freezing, fridge side growing steadily warmer. After a couple hours of much cursing and tool-throwing, I finally found and removed the coil cover and allowed it to defrost (after transferring EVERYTHING to the garage fridge that could be saved, and learning what a nut driver is and wondering how I ever lived without one). Everyone was sure it was the fan motor, but that was working fine. So I put it all back together and hoped maybe the door had just been left ajar overnight.
Six weeks later, it happened again. Less cursing and tool-throwing since I now knew what to do (because I have become the Appliance Repair Goddess), but defrosting every few weeks was NOT a solution. Found an obscure forum on appliance repair with a suggestion to check the door seals. Seriously? Could it be that simple? Nothing is ever that simple!
Checked the fridge door seal and there was a crimp in the back side with moisture collecting on the outside of the fridge when the door was closed, which I'd never noticed because the fridge was black and it wasn't in my direct line of sight at any point in the course of walking around in the kitchen. So I ordered a replacement seal. I have a link somewhere for obscure appliance parts if anyone needs it.
$88 and a week later, the seal arrives in a box. It's heavy and HARD rubber (shut up) and had obviously been sitting on a shelf folded up on itself for possibly years. The instructions/notes said to loosen it up and straighten it out by soaking it in a tub with extremely hot water, or by using a hair dryer and DO NOT SKIP THIS STEP because the gasket has to be flat and flexible when installed. I filled the tub with the hottest water my water heater would produce, and it did not become flexible. I bumped the temp up on the water heater but that didn't work. I filled tub half with water heater water and half with stock pots of boiling water I heated up on the stove. THAT didn't work. I spread it out on freezer paper on the dining room floor and burned up the motor in my hair dryer and that didn't work. Laid it on the driveway on a black towel in the hot Georgia August sun and that didn't work. Called the company back and told them it wasn't happening. They sent me a replacement seal. Same problem. Tried replacing the whole door, but that proved impossible too because Kenmore no longer made that model or parts for that model, so what was out there was it.
In the end, I used super-glue and flex-seal on the original gasket to deal with the problem until I could afford to replace the fridge - it was old anyway.
They just don't build anything to last anymore. Good luck!
