well i just replaced my alternator, what is the volt gauge usually read on ur car... its always been a tiny bit under 13 on mine, now its usually right on or a little more w/ the new alternator...

and i always thought it was supposed to be more like 14... why is it at 13?

 

It normally sits around 14 volts on teh cars I've looked at.
It might be low due to the battery being low.
Did you run the car long with the bad alternator? How charged was the battery when you installed the new alternator?
I always charge up my battery if I have to replace the alternator since the alternator was designed to maintain the battery and not re-cahrge it from a really low discharged state.

 

Mine sits on 13 most of the time.