I can jump my car and it starts but soon the voltage drops. Just replaced the alternator with a 90 amp one. The battery is not new but I was hoping it would be a short other than this battery. The radiator fan stays on sometimes which kills the battery. As soon as I turn on the lights the voltage drops by 2. The new alternator seems to help but doesn't help it run more than a few minutes. The spark plug relay buzzes, I was wondering if that was where the short would be. I don't want to get a new battery yet because in WI the cold will kill it before spring if theres a short in the system. It only gets to be about 12 volts when jumper cables are taken off. I know jump starting a dead battery hurts but I was wondering if you guys could help me out with what this problem is. Thanks