DIAGNOSIS A leaking water pump connection or a cracked drain plug seal. The pump hoses inside can loosen or the silicone drain plug at the back can fail.
FIX Unplug and empty the unit. Tip it back to look underneath. Locate the white water pump. Check the clear vinyl hoses attached to it. Push them on firmly. If the leak is at the back, remove the rubber drain plug, clean the groove, and reseat it tightly.
IF THAT DIDN'T WORK The internal drain pan (a shallow plastic tray under the evaporator) might have a hairline crack from freezing. This requires disassembly to inspect.
HEADS UP Always drain and dry the unit completely before storage. Water left inside can freeze, expand, and crack internal components, causing this leak.