crazy speaker wiring problem need advice

ok i have a 98 eagle talon tsi. i bought it used a few months ago and ive been slowly fixing all the problems with it. im down to fixing the audio problems now. here is my problem.

when you set the fader on the cd deck  to full front speakers the right rear speaker still puts out sound. when you set the fader to full rear speakers the left front still puts out sound. things ive done so far to try to fix the problem are replace the reciever (the old one was a pos anyway) with a eclipse cd3100. i also checked all the wiring at the harness inside the dash with the wiring diagram i got from my all-data pc at work.

so im guessing somewhere in the wire harness inside the dash somewhere there is a wire touching another wire. does anyone have any other suggestions on what might be causing this problem? also am i looking for both the neg. and the pos. wires to be touching at the same time to cause this kind of problem, or could it just be the pos. wire touching and causing this problem meanwhile the neg. wires for the 2 speakers are fine?

thanks for your time and help.

yeah i was going to do that as a last resort but ide rather figure out the problem and fix it if i can. thanks for the help tho.