The fan runs, as you summarized, in response to a T-Stat closing.. now due to the way it is mounted I don't really notice the fan on the Prosine (some comments later) but I also have a converter.. For assorted reasons I prefer it to the Prosine when it comes to doing it's job (The prosine can do it though and do it well. I just like the charge wizard better).
I have seen that fan running (Same type of controller) even though I was not connected to shore power and NO power was flowing into/out of the box. It was OFF, only the fan was running.
Power of the sun