My car didn’t start one day and then got a jump and drove home. While driving the inside and outside lights flickered (almost went all the way out) i changed the alternator and had the battery tested. The connections on the battery are good. Only sometimes the lights will do this then my car won’t start afterwards. When the lights were doing this i put a volt meter on the battery and it went from like 14 volts to 10 volts and back and forth in split seconds. What could the problem be? Grounds? Wire harness? instrument panel? I’m lost.