I am installing a Alpine 9830 in my car . I bought the 87up wiring harness and have soldered all the wires together. I matched them up. Do I solder the Grounds together?? (The black wire that comes from the car to the black wire on the ALPINE. I tried put it on without soldering it I connected all the wires with the 2 black ones and tried it, It does not work. Is their something i am doing wrong??

Did you have a stock amp in the car?