My buddies voltage guage is going up and down and its all stock so he went and replaced it and it still does the same thing. He measured the voltage on it and it puts out between 11.5-14 volts and it alternates. Never did this before I guess so what do u guys think?

 

On the 2-wire plug there is a red wire going to the starter. Check the fusible link on this wire.

 

Have you checked the alternator with a standard multimeter across the battery terminals? Test it with one at idle, revving, and with some electrics on too...once you've checked the fusible link mentioned in Mikes86SC's message, and if you can eliminate it as a problem, the alternator should not drop below 13.5 volts. If it does, it's pretty safe to assume either the alternator or drive belt are at fault.

Si