Audio Systems: Car Speakers, chevy silverado, sony radio

Question
I have a 2003, Chevy Silverado. I have nothing but trouble with the left front speak. The factory speaker went out because it was coming on and off. I also replaced the factory radio and have a Sony radio. When I had the left speaker replaced that included the right since they only sell them in pairs. After the speaker was replace. I started having the same problem. I took the truck back to the dealer and he said the speaker was installed wrong and was shorting or grounding out the left speaker. So, he said that he adjusted the speaker and has worked for sometime now, but now it is starting again. It was both front speakers the other day and I adjusted the volume and they both worked. Then today, they were working fine. I stopped to pick up something and started the truck up and the left speaker would not play. The right was fine and again I adjusted the volume and the left speaker worked fine. The back speaker have always worked. So, is it the speakers or radio. I think that the speaker are the problem in that the rear ones working just fine. What is the answer. Does Chevy have a problem with this Tks Greg

Answer
The problem is that most likely you still have half of the factory system in the vehicle,
when the new radio was installed , did the installer use the correct interface, to make it work with the body control module ?  
interface like this one, this needs to be use if you remove the factory Chevy radio
http://www.oemautosound.com/pc-218-132-pac-c2r-gm24.aspx

was the factory amplifier remove ?