86 GT alternator

[therkel@nac.net]

I installed a rebuilt non-Bosch alternator in my 86 Coupe GT after a 
drained battery left me stranded.  When I flip on the ignition switch now 
the voltage meter reads about 12 volts, maybe 11.5.  After I start the 
car the meter sometimes stays at 12 volts.  A blip of the throttle brings 
the needle up to 13.5 volts until I shut the car off for more than a few 
hours.

I don't think the connections are dirty.  Is the alternator bad, or did I 
screw something up in the installation?
TIA,
John