1988 Turbo Coup is over charging, I have tried several Alternators, batteries and grounded the alternator directly to the fender apron, and it is still over charging. On start up the charge is 12.4v - 12.8v at a direct alternator check, bring the car up to 3,000rpm and the charge goes to well over what my gauge can register(est 18v-20v) this over charging will cut the spark and kill the car. I need help, this has made the car in-drivable, really hate to see it sit.