This problem will occur if the system does not advance into a defrost cycle. The most common reason for it not advancing into a defrost is, the timer. A good way to check it is, to advance it manually. This check must be done when the freezer is cold. It can be advanced by turning the small knob on it, which will be located in a small hole under the control housing. Turn it slowly until it clicks and the unit quits. It's now in a defrost cycle and in a few minutes you should be able to hear some hissing and popping inside the freezer. This will be the ice melting on the heat element. If you hear this noise, it indicates the timer # 63001580 is not advancing and will need to be replaced. It's available at
. If nothing happens, some voltage and resistance checks will need to be made. A technician may be needed to make these checks. I'm listing a site you can check to have a tech come out. Here is a link for the website:
Sears Home Services
. If you need more assistance, please resubmit your question, with additional details.