New Alternator/battery and still have problems

[BaLLLer8]

Hey guys I just replaced my alternator and battery a few days ago and noticed that i'm still having problems. After installing my alternator/battery it read at 14volts which I heard is suppose to be good. After driving the car for about 50miles it began reading at 12.3-12.5 volts. I'm using my HKS turbo timer Type 1 to monitor the voltage. Here are the new symptoms:

-When I open my door the seatbelt doesn't move foward
-When I drive my stereo keeps shutting off
-When I enter the car and insert my key into the ignition the sound that lets you know your key is in sounds like it's about to die (weak)
-My dash panel dosen't even recognize that a door is open

Is there anything else I can check. I am hesitant to drive this car because i don't want to be left stranded. Has this happened to anyone else? Any help is greatly appreciated. Thanks. -Matt

 

[ChicksDigBoost]

Check the Fusiable link between the Battery and the Alternator. It is in the fuse block just in front of the passenger side strut tower.

 

[BaLLLer8]

I checked the the fusiable link and it was good. I've noticed after I turned off my car my seatbelt doesn't retract fwd like it suppose to. It looks like it wants to move foward (inching foward) but after it seems that it loses all its power when the entire cars shuts off. I've lifted the pos and neg. battery terminals just to reset everything and still the problem exist. Any other suggestions guys?