all powered up but no sound

i am installing a Fusion fcd135x in an 05 Impala. i have all the right wires but i can't get anything to come out of the deck. this was the same problem with the factory head unit , i figured that the amp inside of it was bad so i decided to swap it for an aftermarket head unit but i am running into the same problem. with the factory H/U everything turned on and worked but there was no sound. smae thing happening to the new deck. i am using the PAC class 2 data interface and have already found the switched wire. i tested all the speakers w/ a 9v and they all work. then i bench tested the new deck to make sure it wasn't that and it wasn't, everything worked like it was supposed to. any help on this would be appreciated. i'm ripping my hair out over what should be a simple install.   swampy

first of all i made a mistake this vehicle is an 04' and it is a taxi. the vacancy light on top of the car was not hard wired into the car, so it was run through the door jamb and plugged into the cigarette lighter.  after this the fuses kept blowing so the customer decided to keep upping the amperage of the fuse until it wouldn't blow, i think you know where this is going now....eventually the wires couldn't handle the amperage and fried the wiring harness from the lighter to the fuse panel. in doing this, it melted several other wires together. the vehicle was not under warranty so they gave us the job of changing the harness. now with that said, we took the car to the dealer thinking the head unit (factory) had to be reprogrammed. they said that there was a shorted speaker somewhere and the head unit was fine. i took apart the dash again and found nothing. i also checked each speaker from behind the head unit and everthing was fine. each speaker popped with the 9v battery and i did the beep test for continuity with my volt meter and it was fine. i'm just stumped....... swampy

Ok that clears alot of things up. Here is what I would do. I would take a known working head unit close to one of the speakers. I'd run temporary power wires to it straight from the battery would be easy. Then I would unhook the factory wires from the speaker and run short ones from the head unit. This should certainly tell you if the speaker is working. (Make sure you check balance and fader settings if you don't hear sound right away. If all is well  I think I would just rewire.