I just tried installing a JVC head unit in my car, and lo and behold, as soon as I hook up all the wires, nothing happens. I double checked the wires with a voltmeter and I'm getting ground, power, acc power, where and when it is needed. I'm about 95% sure I have the speakers hooked up correcly. Am I missing something obvious here before I make the drive across town to the authorized JVC service location?