My LG refrigerator Mod#LRFC22750TT will not go into defrost and freezes up with white snow build up. I suspect the main board or the defrost sensor. I do not have a manual. Ihad the freezer back off and Isaw the evapator fan working when I pushed the door switches in. I tested the ohmes for the heater and that is good. Could someone give me a tip. My email is joel.jeffers@gmail.com