alternator wiring diagram

I have just bought a 1982 chevy pick-up with a 400sb and i was looking at the voltage to the battery and noticed it was around 8 volts. I took the alternator in and got it scanned and it has 15 volts, so i know that it isn't bad but i don't know the wiring diagram of a alternator to see if i can find a short in the wire maybe. could somebody send me a pic. of where the wires run from the alternator.

Did they test the amperage output? Sounds like you may have some shorted diodes in the alternator. When the amperage demand is higher, the voltage will drop.