@stereo5, not true I'm afraid. All MC told us was something we know already. The system makes a pop when the car is turned off. He did not tell us why. Karzuu, it sounds to me like one of your units is incorrectly wired perhaps a grounding problem/loose wire. I'm sure if you go to a reputable car system's installer they can figure it out for you. Try turning the volume all the way down before you turn off the car. Pop just as loud?