I am having terrible problems with 2 different hovabators. I called the manufacturer and the women I spoke to was very tight lipped. I had to pry information out of her. My Hova bator 4200 is a replacement for a cheaper model that I struggled with for a year which kept killing my chicks near hatching time. I have a digital thermometer that reads lowest and highest temps. This morning the range went from 103 to 97.4 . This has been happening for the last 12 days. Their website guarantees the incubator for 1 year and a paper that came with it says it is guaranteed for 30 days. The woman verified that the new guarantee is for only 30 days. She said there should not be any fluctuation in the temp. She also said that's why we say to run your incubator for 8-10 days before adding your eggs. The directions that came with it said to run it for 6-8 hours before adding the eggs. I would say if I run it for 10 days then hatch for 21 days my guarantee is invalid. So. I am surmising they are having trouble with their thermostats and want to unload them. I am going to ride it out and return the incubator. I am going to try a Brinsea.