It is a Kenmore, and the freezer is inside the refrigerator. The freezer box/compartment is a hallow metal drum type of contraption with a flimsy plastic door, situated inside the refrigerator at the top. Beneath is what I believe is a drip tray. I think the freezer box cools the entire unit. I don�t see modern refrigerator�s built this way.
So the refrigerator can maintain cold, the freezer metal drum has ice on it and for the most part it seems to work during fall to spring. Then summer came and the freezer compartment starts to ice up. I thought it was the increased humidity but the seal seems fine (acknowledging that it may not be as air tight as it can be despite how it looks).
The whole unit only has one dial and it is a simple dial that goes from off to A, B, C, D, Hi. I tried lowering the setting but that just seems to slow down the ice build up, not completely stop it. The freezer compartment has no controls. In the back there is a side-mounted small red hallow tubular intrusion into the freezer that I have no idea what it does.

Is there anything I can do to fix this myself? As you can imagine this ice build up is quite annoying.
Would a further decrease to the dial setting work?
Given a choice between calling a repair man and buying a new fridge, I�m tempted to buy a new one but I like to salvage it if I can.
Thank you
Bob