DIAGNOSIS The defrost drain is clogged. When the freezer coils defrost, the water can't flow down the drain tube and overflows into the fridge compartment.
FIX Clear the clog in the drain tube at the back wall of the freezer.
1. Remove all items from the freezer and locate the small drain hole in the back center wall (often under a small plastic cover).
2. Use a turkey baster or funnel to pour hot (not boiling) water down the hole to melt any ice blockage.
3. For a deep clog, use a long, flexible drain brush or a straightened plastic coat hanger (carefully) to gently clear the tube. Don't use a metal hanger—it can puncture the line.
IF THAT DIDN'T WORK The clog might be where the drain tube connects to the evaporator pan underneath. You'll need to pull the fridge out, remove the back access panel at the bottom, and check the drain pan and tube connection for ice or debris.
HEADS UP Prevent future clogs by ensuring your freezer isn't set too cold (recommended is 0°F) and by doing this clean-out every 6-12 months if you see moisture building up in the freezer back wall.