I recently had similar issues with my cars factory wiring harness. I traced it to the blue wire which was melted under the dash. I eventually traced that to a pinched blue wire on my ignition switch. Yes, my car would run mid to high 14v and sometimes spike up above 15v. At the time I thought I had other issues because of the erratic readings and I replaced my alt and regulator which didn`t help due to the fact it was the blue wire shorting out. It toasted my red top opitima.