Alternator should not be an closed circut. Lots of hot rods run one wire alternators. Thats how you wire them...straight from the battery. Logic would tell me they are asking for an additional wire to feed it more volts. But as some one said above adding an additional ground helped alot so maybe they meant a ground?? Im shooting in the dark.

 

So happened to have an electrical engineer come by my office this morning on an unrelated matter. He said he thought it had to do with getting the full efficient amperage out of the alternator. Said it would work fine without the additional cable, but the amps would be lower than rated & the alternator less efficient without the additional cable directly to the battery. He also told me I'm better off practicing law, finding a mechanic, or buying a car with a locking hood that I don't have the key to :0