I just bought the Jensen vm9312 and to make sure it worked I asked my friend to connect it to his wiring harness to see if everything works. Evrtyhing worked except no sound was going tru the speakers and his system. We connected his unit back on and HIS unit worked just fine. Please help with waht I can do to fix it. Can I some how convert the wires form the speakers to RCA outputs and in puts or WHAT???!!! tks