From my meager knowledge, your best bet is to start at the source and check for problems working your way down the line. Start at your head unit to see if it's putting out signal. If so, check your lines at the amp to see if you have signal there. Then check the output of the amp, so on and so forth... Sounds like there's a fuse you're missing or something, I'm really too tired to actually make my brain think about it right now
