I'm Charles from Illinois, and I purchased a 2000 Mustang from my cousin a few months back. He had a aftermarket head unit in it which he snagged before selling so I installed my own aftermarket head unit, and all was well except the lower door speakers didn't work. I searched the web, and could not find my problem, or a path to take, so I dove in head first, and started seeking out the issue myself. I found a defective amp under the drivers side rear deck, and decided to pull it, and was going to seek out a salvage unit, but I decided to have a poke around inside the amp before buying the unit. I'm glad I did, and I came here to just let others know what I found and how to fix it. All that will be in another post in a more appropriate location.