I had my 5 channel alpine amp installed last week and the shop told me it had a bad rear channel. I tried putting both rear speakers on channel 3 so that there would at least be some signal coming out of both rears. There is still no sound coming out of the rear right speaker. I don't really know what I am doing...was this not the right way to go about doing this? Or is there another wiring problem somewhere else in the car? Thanks