Generally what happens is: the cap tube has become separated from the suction line. Out of the factory the small tube you see running beside the bigger one is soldered together and the heat off the cap tube(small one) keeps the temperature of the bigger one(suction line) at a level that it wont frost up. Well over the years the solder breaks from corrosion and separates SOoo...what needs done is..... The two refrigerant lines need bonded back together. Remove the top screws holding the condenser to back of frig leaning it up against a wall or something so it doesn't totally fall off and get kinked or broken. Totally strip all the old insulation (using utility knife and one cut vertically all the way down will do it).till it's bare copper, as close to cabinet where it enters freezer section on the outside.if you see the cap tube loosly hanging there and not welded to the suction line Take some black tape and as tight as you can wrap it tie the two together all the way down.then take some plumbers pipe wrap insulation tape and insulate the tubes down to machine compartment area or use some 3/8 armaflexx that is also used for tube insulate in HVAC. Also put some putty back in where the tubes exit outside to keep warm air from going inside freezer.. put it all back together and your done.