2011 chevy charging

[psuedopimp]

okay there are alot of people on this site that do this for a living. not me. but i was fortunate to receive a new 2011 chevy as a work truck. i personally own an 84 K10 and a 2001 tahoe. i have had the truck since tuesday and noticed last night that the charging guage goes down to about 11-12 instead of the normal 14. i didn't know if this was normal with some type of high tech charging system, or if the alternator is already going out. i have only put 650 miles on it. of course the saleman didn't know anything and they don't have techs in on saturday.