The fuse link only blows if there's a massive short somewhere. Disconnect the output wire from the alternator (if it's got one) and the wire from the battery cable connection at the starter going to the ammeter. (That's probably the fuse link, right?) It sounds like you've got a BIG 12 volt supply wire connected to ground, like maybe the one to the fuse block, or a shorted-out alternator rectifier.
Jerry