Fridge was getting warm while the freezer was cold and running constantly.

After testing and eliminating the temperature control and the timer as the problem, I turned to the thermostat. I had to wait for the ice buildup to thaw and then could remove the rear freezer panel (this was the 3rd time: first, to discover the ice buildup causing the problem, second when it came back after a complete thaw and test the thermostat, and this time to put the Partselect thermostat back in). My thermostat was visibly damaged from water melting into ice and expanding the casing and eventually breaking one of the connections. I connected the thermostat connection wires (not recommended) to get by while ordering the part, which shipped faster than local repair places could get it from their warehouses, and at a fraction of the cost. I'm really impressed with partselect's fast service and all the knowledgable customers who have explained how they installed them. I now have an intimate knowledge of how my fridge works and saved hundreds in repair, or twice that in replacement. Thanks!