When I bought my first batch of I-Techs I set a few of them up at home so I could play around with them. I noticed that the fan in one of them (an I-Tech-6000), would swing into high speed with no signal present. After several minutes it would die down to a low and quiet speed. Then it would repeat the process. Again, with no signal present, and all faders down. In the quiet of the room I was working in it was very noticable. It was in a rack with two other I-Techs, which were quiet unless I pushed them.
I don't know about any specific temperatures that were present, but I think fan speed is governed by temperature.
I sent it to Crown and they fixed whatever was wrong with it and had it back to me within a week. I remember being impressed at the turnaround time. They made a note about replacing an input section or something. Whatever was wrong with it might have been commonplace with those early I-Techs. That's just a wild guess, based on the fact that they fixed it and had it back in route to my shop on the same day.
That was quite a while ago and I haven't had any trouble with it since.
The amp was doing it's job, but I knew something wasn't right with it. I wanted to take advantage of the warranty while it was still covered. As it turns out there was indeed something wrong with the amp.
I hope this helps. Take care. Jeff