This problem started a few weeks ago. I figured the regulator was on it's was out. A couple of days ago the system stopped charging all together with battery idiot gauge lighting. Just put in a rebuilt AC Delco alternator and I'm still getting Voltmeter readings of 18 (sometimes), no battery light though. I recently changed the MAF relays (made a big difference), but the high volts started before that job. This is a stock 1988 coupe. Any thoughts out there?