I'm brand new to car audio and just replaced the factory setup in my 1995 Ford F-150 with a Sony cdx-sw200 HU, two 6.5 inch Sony speakers in the front and two 6 x 8 Pioneers in the back. When I start the truck everything is fine, but there is a static noise that begins once I drive for 1 or 2 minutes. This is present whether I'm playing a CD or listening to the radio, although its more high-pitched and crackling on the radio and worse with AM than FM. The noise does not change with the engine's RPM's. I've checked all the connections and the only thing I've found is that it goes AWAY when I disconnect the black ground wire. I'm afraid to leave the ground wire disconnected and am not sure where to go from here. Please help. I beg of you.