2004 Kenmore Coldspot 10674269400 Top Freezer

Hello,
Hoping somebody can help with this dilemma. The freezer seems fine - freezes to below zero. The Refridgerator will not cool lower than 50 despite set to 'coldest'. The evaporator coils in the freezer were not frosted, the fan motor in freezer works, the fan seems to be turning fine. We have continuity in the evaporator heater. When the panel was first removed to look at the coils, the diffuser was full of frost. We're not sure if we should be looking at a new electric control (with the defrost timer) or a thermastat. Any help would be appreciated.

Thanks,
Scott

Does anybody have experience with something similar along with a problem in the electronic control or thermostat? We could just replace them see but we were hoping to hear from those more experienced. Thanks.

Melissa