Probably not defective. I have an older Hovabator with a fan, and I have a similar problem, just not as bad. The thermostats they use are notoriously touchy. Mine does very well once I find that "sweet spot"Hi everyone. I have a question about one of my incubators. It's a hovabator still air. I got it brand new and brought it home and turned it on for a dry run. I cannot get the temp to stay the same. It's either too hot or to cold it does not matter how little or how much I adjust the thermostat knob. It sucks. Does anyone have experience with this? I'm going to put a fan in to circulate the air to see if that helps. Do you think I have a defective incubator?