I've noticed that when my Mac was in sleep mode when I first woke up today (sleeps all night) that the fan was running some, keyword some. I read up on threads where the fan was constantly running during sleep but this is not my case. It would run for a 10-15 second interval in which the LED light that indicates the computer is sleeping would stay at the brightest setting. When the fan stopped the light would continue its phase of bright to dim. Any ideas as to why this could be happening?