I have a 1985 Berlinetta 305 carb'd. Have had battery going dead on me, almost like the alternator isn't charging the system. Bought brand new alternator and battery, just to eliminate any potential problems. When I went to disconnect the alternator, it has a 2 wire harness that plugs into the alternator. One wire, black, I traced and it leads into the battery. The other wire, red, is hooked onto the battery section of the alternator. It looks like it had been cut and spliced to be shorter.......my question is, where is the red wire supposed to go and would that give me a low voltage reading on my alternator using a multimeter? The original alternator was tested, and was showing good. I hooked it back up how it was originally. I can post pictures if that will help at all. I need to get it fixed pretty quickly cuz I am going out of town and the wife needs her to get around during the week while I am away.

 

Large red wire would go to BATT stud.
Smaller gauge wire, ign key off, reading battery voltage, would go to #2 terminal - voltage sense, this wire. Usually connected to fuse panel, maybe.
Other smaller gauge wire, key on, ign voltage, would go to #1 terminal - excite voltage, turns on alt.

There is another place to check and this would be at the solenoid terminal on the starter. There are a couple fusible links connecting onto the stud with the positive battery cable. One lead is power supply for the car, the other is from the alt BATT stud. If there is a poor connection here, no battery charge, use a wire brush to clean. Also, check the fusible links making sure they are making a complete circuit.

 

Yeah, post pics if you can. Your car's original alternator had 4 wires going to it, not 3. Somebody may have messed something up.