Jesus Urquizo

Hey guys, recently my 07 avalanche has been making a whirring noise when accelerating or upping the rpms. It won't make it right away but perhaps maybe 10 mins or so into driving I'll notice it'll make it when speeding up from 0 to about 60 or at lower rpms. Also my batter gauge usually stayed in the center and sometimes it'll lag to the lower side but stay in position. Currently it only has one of the 2 fans working. Could it be the fan? A pulley on the belt system? Any ideas? Also my check engine light has not come on and it is not overheating.