I have a problem w/charging battery. Just changed alternator, old one blew the bearings. I've checked the main fuses and the 20amp in the line all okay. the battery light on the inst. panel does not lite up with the key on and engine off. I know you have to get 12v. to the alternator fields to fire it up but don't know what/where I'm missing it. Any help would be great, it's a 97' F150 Lariat.