When I turn the key to the ACC position and the cd player comes on, all of my speakers have a high pitched whine, even when the cd player just showing the clock. It started today when my rear speakers werent tightened in all the way and one of them fell back into the hole and may have shorted out on the metal. I thought it was the rca's so i replaced 2 sets of them and it did not help. i also tried disconnecting each speaker, one at a time to see if it fixed it, this did not work. My front left speaker isnt playing at all (just the high pitched noise). I also tried sanding down my ground again. Do you think it is the HU? I am about to get a diskman and a headphone jack to rca cord and plug it directly to the rcas to see if it is the problem. Does anybody have any other suggestions.