I have a small 176 4 channel amp (6mos old), 2 3way kenwood 6x9's, factory 4's and a small sub. My problem is I recently restored my blazer and tried out the system in my empty interior (It was working fine b4) - It was fine. Now that I have all the seats in and carpet etc. and the rear channels do not work. I did some wiring tests and found that the problem is within the amp. I took it all apart and no signs of burning or loose connectors - any ideas?