99 Gransd Am /Cavalier alternator
 

After removing the alternator and getting it tested my helper noticed the black plug was missing. We bought a new on at the local auto part store but we prolly wired it wrong. There is a gray wire and a red wire. We wired it up the way the schematic said but when we started the car no voltage. Which pins do they go on. There are 4 pins on the alternator four wires on the new plug two which are not used, where do the red and gray wires go. Thanks in advance.