We bought my wifes aveo used, and the rear speakers did not work with the stock head unit(from what I remember). I surprised her with a new head unit(mainly she wanted the aux input for her ipod). I bought a harness adapter to make it easy/clean install(in past vehicles I would splice wires). The new connector from ebay was screwed up and ended up taking me hours to figure out what was wrong(I think there was a wire/clip in the wrong socket or whatever and I figured it out and moved it and it worked).....sorry this was a few years ago don't remember everything exactly...so when I first hooked the new head unit up I believe ONE of the rear speakers started working...weird! So now recently the volume has been cut in half for some reason...we used to listen to the radio at audio level 15 or so, lately it has to be on 30 or so to hear it at the same level....anyone have any explanation for these things? The head unit was a $55 or so dollar special from walmart if I remember correctly.