I have a older model GE refrigerator (TBX25RKB) (conventional top freezer) that I keep in the garage for drinks and overflow freezer space. I noticed a few days ago the beer seemed warm. Checked the freezer and everything was frozen. Turned freezer and refrigerator to coldest settings. Today I put a thermometer in to see temps. Refrigerator was 48 and freezer was 19 degrees. The unit is running and the fan is circulating air. Any ideas on the problem. Could it be low freon? Is it worth fixing?