Fan does not spin at all. Is that normal?

The fan of my WD TV  Live Hub does not spin. Yesterday I watched TV via the Hub, and I live in Hawaii. The Hub was pretty warm but the fan didn’t do anything. Does it only start working when it gets really hot? Or should it always spin? How do I know if it works correctly, before it all me melts down:cry:

I think that it spins according to internal temperature, but I don’t know what the threshold is.  

I do know that the HUB will put a WARNING up on the screen if the internal temperature exceeds something like 60C, and will shut down if it gets a warmer than that.