fridges especially auto defrost ones, have a trough inside, a pipe runs from that out the back and into a tray around the compresor. as the compressor is usually hot, intermittently, it then evaporates the water. Check that the pipe from the trough, in the back of the unit, is clear to the outside, piece of wire pipe cleaner etc should do. Nothing to hard, do not want to damage the pipe.
SD
November 2011