With an old GE refrigerator, when we had ice buildup with water leaking into the fridge, the problem was a clogged drain tube and was easy to fix, since the tube ran down the back of the case. Now with this newer Whirlpool, there's a lot of ice in the freezer and the food compartment is warm. I took off the cardboard panel on the lower rear and found that the pan was dry so I thought that maybe the Whirlpool also had a clogged drain tube. But with this fridge, there was only a short tube that seemed to come out from below one of the refrigerator drawers.

My second step was to try to remove the rear wall of the freezer compartment. I pulled off the air control knob and pressed the 4 tabs holding in the air tower, but I couldn't get it off. Is there some trick to it? There seemed to be styrofoam behind it. Once I get the air tower off, there seemed to be only 3 screws holding the rear wall in place. If I manage to get the rear wall off, will it be obvious whether the drain tube is clogged and how to clean it? Any other advice would be appreciated. I guess if the problem isn't a clogged tube, it could be a bad heating element or timer. Thx.