Freezer coil frosting up solid. Refrigerator warming

First - I asked a person familiar in ref/freezer repair for assistance. This was the hardest issue - trying to find someone to offer "free" advise. He stated that when this problem occurs it is usually one of two things: 1) The defrost timer (underneath Refrigerator - Attached w/2 screws and plug-n connector) not functioning or 2) The defrost sensor (clipped-on to the coolant line (2-press-on wires) above the main coolant coil in in rear of freezer section behind panel secured w/5 1/4" hex-head screws) not properly sensing need for defrosting. The Tech. also stated that the defrost/heat coil, which surrounds the large coolant coil in the back of the freezer hardly ever goes bad unless it is the glass/clear type coil which often crack. (Mine was the black filament type element like found in an electric oven). I check the element with an ohm meter - 27 ohms of resistance which indicated it was okay). I replaced both defrost timer & defrost sensor at the same time and that fixed the problem. Parts ordered were an exact match to originals (dispite model number changes/upgrades) and everything went very well. NOTE: It is good to have the part numbers off of each original item and know what they are called before placing your order. All fixed for less than $50.00. A service call alone would be more than this. Took about 2 hours to do, due to having to defost the iced-up freezer coil w/a hair blower. Don't use sharp objects to chip away ice, let the blower do the work - Patience and a couple of towels to absorb water is important here. Hope this helps the other do-it-yourselfers.