So I recently picked up a 96 tahoe (4dr), when you try to turn the volume **** up it will go down, and down goes up and vice versa. Its really annoying, and I noticed that my AC unit when its turned all the way down will sometimes make it work perfect. But when its on in any way it has the previous mentioned issue. I also recently discovered the rear speakers do not work either. Every bit of info points to my amp or a short, everyone keeps telling me to use the "pink wire from the other harness" but its BUILT into my harness. Meaning powering the amp isnt the issue. I would like to believe I have a short somewhere or frayed wires? and maybe someone can at least tell me where to start. Never touched car audio in my life and this has me scratching my head. Just need some advice on where to start.

 

is it the original stereo?

the **** contacts are probably dirty. Try disassembling the unit and cleaning them out with electrical contact cleaner. There are tons of videos and websites how to do this.