I have a kenmore/coldspot refrigerator freezer and it keeps freezing up

I have a Kenmore/Coldspot Refrigerator Freezer Modle 106.72134101. My problem is the freezer pan keeps icing up solid and also causes the overflow duct to the refrigerator to ice up. I defrosted it and it is icing up again. So it must be that the automatic defrost timer or the defrost thermostate is not working. Also, I have no power to the defrost heating element but it does ohm out to about 30. More so I can not locate the defrost timer to test it and I am unshure how to test this.
Thanks tony

It may be that the power only appears at the element when it is being defrosted. Some refrigerators only go to defrost mode when the door hasn't been opened for a few hours. Mine always defrosts in the middle of the night. Tape or place an ice cube against the wall of the freezer. If it shrinks considerably overnight, the defroster is working. If it hasn'r melted at all, the problem is the defroster.

If the tube that drains the water out to the bottom is stopped up, it would produce those symptoms. Pour some water in the drain duct to make sure it is draining down to the evaporation pan. If the tube is stopped up with mold, Clorox bleach will free it.

Make sure there isn't a signifigant air leak in the door seals. More humid air means more ice buildup.

If you have an "energy saver" switch, try running it with the switch in the opposite setting for 24 hours to see if that makes a difference.