I noticed frost buildup on the back wall of our Amana bottom-freezer refrigerator the day before yesterday. It seems to be running all the time without cycling. I had a similar experience with a different refrigerator (top-freezer) which turned out to be a burned out (?) element that melted the ice during the cycle.
Anybody got any ideas?
Thanks.

Your defrost system is on the blink. Usually the defrost timer,defrost bi metal thermostat or defrost heater is causing the problem. When repairing a refrigerator that has this problem I usually replace all three parts to prevent more problems in the not so distant future. One other item to look at is the fan that blows inside the freezer. If it is not working that can also cause a frost up problem.