So my 07 tahoe LT has gone through 2 alternators in the last 3 months. The first one was the original from the factory, so I'm not too surprised on that one going out. The second was a remanufacterd duralast Delco alternator. And that one went out after 3 months. Have my 3rd one on it now, and it's dropping to 12.8 volts after driving for about 15 minutes. When I turn the truck off and back on again, it goes right back up to 14.6 volts. If I turn the AC and radio off, it doesn't help. I'm sure I need a new battery as well, but sadly, I don't have the money for it right now. Checked the grounds, and they're all good and secure, but I'm not sure why my tahoe is having so many electrical problems. It does have an aftermarket stereo with the stock head unit, but if that was the problem, it shouldn't stay at low voltage when I turn the radio off. So my question is why does my voltage keep dropping to 12.8 volts and then going right back up to 14 when I start the truck back up?