Whine problems

Had an interesting problem todau on a Jeep Cherokee install. I installed a CD player 4 speakers, 2 amps and a 15" sub and when everything was ready to go I put the fuse in and.............( BTW: this was used equipment that the customer brought to  me to install ) and everything worked except the front driver side speaker ?? First I thought I sisn't hook up the back of the speaker correctly so I took off the door panels and looked and the solder was still good. Next I checked the back of the amplifier for any loose connections at the speaker terminal and nothing.... I was getting continuity between the (-) and the (+) of the speaker. So off to the head unit and the connections there were all good. I tried to swap the RCA's ( these were high quality ones too ) between each other and there it was !! The stupid RCA on the left side was not working. I checked for a signal on the left RCA and nothing there. There RCA's were flawless when I connected everything together and there was not break or cold solder in the head of the RCA's. So I went and replaced the RCA ( not cheap ones either ) and the problem went away and off goes another happy cusotmer booming away down the street Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

Thanks for all the tips guys...the prob was grounding, though the cheap rca cables have been replaced too so that was entirely possible...i ran new frame ground upgraded all ground cables and power wires and reran all hookups away from each other(power,spkr,etc) thx again

I also just now started experiencing alternator whine with my Honda. The weird thing is that I've had my stereo for about 4 years now, and it just now starting making noises...and the noise is bad! Any suggestions on why it just now popped up?