Did you double check the wiring at the headunit side to make sure everything is plugged in correctly?

 

Yeah I checked it. I asked for advice on this problem a long time ago actually. In the beginning the problem was hit or miss. One side was extremely low. There was sound, but it was barely detectable. The problem would come and go randomly. If I started the car and the speaker was working normally, all would be well. If I started the car and it was not working, it would remain that way until another restart of the car.

I tried to figure out a common denominator between starting the car and the problem. The only thing that I could think of was that the original installer (not me) grounded something to the parking brake. I chased cable and found nothing wrong.

I reversed the RCAs on the amp and the problem switched sides. I assumed (key mistake) that since I had some audio and the problem followed the change in wiring that the amp had a bad channel.

Eventually the problem became full time and I could no longer hear any sound out of the malfunctioning side. I assumed (2nd mistake) that the channel had finally kicked the bucket.

Today I replaced the amp. I still had the same problem. So I took the RCAs for the front and rear left side (malfunctioning side) and plugged them into the front left and right. I had no sound. I then reversed it and plugged the front and rear right side (working side) into the front left and right on the amp. I now have sound in both sides. As expected, if I fade the radio toward the front or back the sound fades left or right (due to the intentional wiring).

My new assumption (probable 3rd strike) is that the left side channel in the deck is dead. I have functional audio again for the moment, so I can live with it. I will pick up a new head unit as soon as I can secure funding to go all out with S-Pods and Focals.

Thank you to everyone that has helped me during this process. My car audio education has come from reading the walkthroughs/threads in this forum.