Changed alternator and battery. Now have problems

[ciGARRETTsRbad4u]

First of all, my car is a '90 240 with a '97 '98 twin cam if that makes a difference.
My alternator went bad so I switched it out along with the battery at the same time.
When I started my car, I noticed the battery light in the gauge cluster was on, which was not on before when the alt. was bad.
I believe the alternator to be good because the car will run with the battery disconected. When I rev it up a little, the battery light will flicker on and off.

Not sure if this is related, but when I started the car, I also noticed a kind of buzzing sound from under the dash which was caused by this plug under the driver side kick pannel. When I disconnect it, the sound stops.
(sorry for the sideways pic)



When I disconnect the alternator from here

the 'buzzing' sound and the battery light will turn off.


Any ideas? Any help would be greatly appreciated. Thanks