Soo I've been having this problem for about a month now! Started out my battery light on the dash would flicker randomly while I was driving home one day, no rhyme or reason as far as accelerating/braking or hitting bumps. After getting the battery and alternator tested i bought a new battery and positive battery cable to match because of some corrosion and a dead cell. Also got a new serpentine belt just in case it was slipping. (Just rrplaced tensioner in feb, water pump and timing belt in dec). Now 3 weeks later the freakin light starting flickering again this time accompanied by air bag light on dash and lost power to my headlights while driving and every single dash light came on for like 10 sec, but everything else had power as usual. Go straight to AutoZone when I got off and had my alternator tested again and the dude said it's pushing out right under 12 volts. So I figured that was ok right? That's what the alternator should charge at right? I check my grounds and replaced negative battery cable to the chassis? Now it starts up like a champ and while I'm driving it'll flicker still but I did die when I let it idle for like 10 min but started right back up a couple min later? Alternator or something else???

 

It should be closer to 14

 

12V under load is way too low for a properly functioning alternator. A battery not under load and not being charged should be right at 12V.