I recently replaced the defrost heater element, something I have done in the past with this refrigerator. The heater element I was replacing was single element, but the replacment part I received was double element. I replaced the old element with a single element taken out of the double element unit, because it seemed to be exactly the same. Now a month later, the freezer has frosted up again. Should I have used the double element unit, or should I have had a different, single element replacement part? If I should have used the double heating element configuration, do you think I can take the single element that has been in the refrigerator for the last month, and put the original double element unit back together to use?

Thanks for the very useful information! How do I check to make sure the defrost thermostat is working?