My GE side by side refrigerator/freezer won't stay cold enough. The freezer stays in the 20's and the fridge in the 40-50's. So I unplugged it for a day and let it defrost and cleaned it out. I plugged it back in and it worked and the temps went down to where they were supposed to for a few days until some snow looking ice built up on the whole back of the freezer and now it is once again not getting cold enough. The fan at the bottom of the back is working. Other than that, I am not sure how to troubleshoot.