LG frige model #LBC22518ww. Freezer works. frig is not coolong after a few hrs #s 567 go on and no air flow to frige section. Evap fan is ok. Air will not flow to frige when door is closed. When door is open, you can feel the air in frige. Possible return air restriction. After a few days ice builds on evaporator. Heater is good. replaced main module thinking defrost timer was in board. Please help.