I'll have access to the box tomorrow (it's in another town).
wingnut, the defrost cycle must be working, at least to some
extent, or it would not produce the large amount of water
that drains down in the the 'icebox' portion. i.e., the
frost/ice is melting.
In googling the problem, it seems that most new designs
do have a metal plate or wire carrying defrost heat down
into the drain line. This unit does not. I'll fabricate
something out of 12 gauge solid wire if I can't locate
the correct part in short order.
Thank you for the replies, folks. I'll give it a shot tomorrow.