95 civic electrical

[91 tsi 95 jdm]

i tried hooking up a deck to my civic and my constant wasnt working so i hooked up the constant and firewires from the harness to the deck all together. after driving the car for about 15 minutes the deck kept turning off then restarting. Then the turns signals stopped working and the car died. after about 10 minutes it started then it died again. i got it boosted then it died again. got it boosted again then after about 5 minutes of driving it died again. would any of this have to do with how the deck was hooked up or is it the alternater. the battery is brand new.