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What you can do with your volt meter is Take the Red lead on the meter and put on the big Orange/Black wire for the Alternator(s). Take the Black lead from your meter and touch it to a ground like the battery or engine block. You should get 14 volts if the alternator is good. This is an easy way to check which alternator is not charging.
Well, My material for Ford is down right now. But I will let one of the other Experts help you out.