Check your starter.
Yep. Once your AC starts showing a different temp than you left, it's time for a new battery. I got the AGM Advance Auto platinum or whatever. Seems to be holding up well.CCorbin1030 said:It's your battery. I was having the same issue with my 2010 Sierra. It would sluggishly crank a few times then fire up. One thing I noticed was that my air was always on at 74 or 78 degrees(one of the two is factory set I just can't remember which) even if I didn't have it on when I shut off the truck. Took it to Auto Zone and sure enough it needed a new battery.