Kenmore 253.5569340N not recovering/cooling well

[Pacochu]

I have a 2005 Kenmore side by side 253-556934N fridge as our garage fridge. I dragged it down the street 10+years ago when a neighbor put it to the curb when it stopped working while he was out of town. I replaced a temperature control and got it working again. It's served us well in that time. I've replaced the control board, the water valve and maybe another part or two in that time. But now, it's acting up again and I don't know where to go with it.

Last week, I went to grab something out of the freezer and noticed it was soft. I transferred everything to the house fridge and big freezer and left it unplugged and doors open overnight. I plugged it back in and left it closed without food in it. It took the majority of the day to get to -5 freezer/35 fridge with the dials set at 6 or so. With food back in, it hangs at 40-41 degrees, even with the dials tuned to the coldest settings. The freezer stays at 0 degrees or below.

The coils are not frozen up and the defroster works. Both the evaporator fan and the fan leading to the food compartment are working. The damper opens as I can feel cold air flowing into the food compartment. The coils in the back are clean as I just brushed them off when I unplugged the unit. That fan works as well. 

I assume the problem could be possibly the temperature control or thermostat or the damper not opening all the way. At some point, I don't know how much more money I want to put into a 17 year old fridge. Also, it's currently 100 degrees here in Houston, and my uninsulated garage probably is not the ideal environment for a fridge. But even overnight, the fridge doesn't get back to 35 degrees by morning.

[16345Ed]

What’s evaporator frost pattern look like?