frezer is frezeing up in back of frezer compt.ice on all coils top to bottom.have replaced defrosttimer so far. i can unplug refg. and defrost it plug back up works perfect.makes ice will freze. til coils ice over again.haven/t thermostat yet.thinkinking of replacing heating elements and thermonstat as complete unit. WHAT DO YOU THINK. defrosttimer is working great.