so i bought this 2004 s4 about a week ago, the guy had 2 amps and his 12" sub removed before the sale so i have some excess wires hanging out in my trunk. the stereo is constantly making this humming sound, (my friend said it has something to do with the ground from the stereo?) this sound is on whether the car is on or off, key in and out of the ignition... i unpluged the wire that runs to the amps which no longer exsist but the sound is still there. anyways my battery wont stay charged now and it clearly has something to do with this humming sound any ideas guys??? i'm clueless. i just need a quick fix before i take the car in to get the stereo work done. thanks!
-Bud

 

just check the battery cable/terminal for any other power wire and eliminate it.