Re: 1966 Mustang ammeter problem
The Yellow wire turns into a Black/Yellow wire once it goes through the bulkhead connector (center one, not the one above the master cylinder.) The Black/Yellow wire goes to the battery side of the starter relay, and to the Batt post on the alternator. If the battery is connected, you should be VERY careful probing it, it has full battery voltage all the time. There are 2 connectors before it gets to the alternator. One is a single wire, and one is the 3-wire connector off the alternator. You could disconnect the battery and check the continuity through those connectors. Whatever you do, be REALLY careful when the battery is connected. Wiring diagrams are available from all the vendors, they can just be a little tricky to read. Hope it helps.