High battery voltage

[1slowdsm]

I finally got the alternator out, havent been driving it since Monday when it started to constantly run 18v minutes after starting. I took it into Autozone to get it warrantied and the guy who helped me did a couple quick tests on the machine and he said it passed and tells me it's perfectly fine. Then he says he cant give me a new one 'cause it passed and he'd be losing money if he gave me a new alternator. So I leave and call up the Autozone that I used to work at, talk to the manager and he's like "Yup, you're voltage regulator is going out and they should've warrantied it." And tells me to stop by and they'll give me a new one. Just like that, quick and simple. I sure hope it doesnt turn out to be a shorted battery tho...I'd rather have the alternator go bad than the battery.