s14 dying

[xsublimefrekx]

i am having problems with my s14. Last week i redid my harness in the driver side fender because it got a little chewed up, everything went fine. Yesterday my car died while driving it, i brought the batter to get tested and they said it was no good so i got a new one, same thing happen today. I bought an alternator off of a running car and installed it and the same thing happened. When i drive the car is good for a little bit then the radio dies, then headlights, and then the afc starts to die and the car runs like shit till it just dies completely. I dont know what else it can be, i have to check the grounds for everything tomorrow but i dont think its that. Any input would help a lot as it is my daily driver.
Thanks