I have a pioneer stereo, wired through the factory plug with an adapter. Just recently, when the stereo is turned up just a bit (not loud at all) the trunk indicator turns off and on but I can leave the stereo on and volume down and its fine. I turned the AC and lights on to put a load on the battery just to see if that was it but it didn't make the indicator go off and on. I went over bumps to see if it might be a loose connection...nothing. Any ideas?

 

figured it out...its the stupid glass break sensor for the alarm...needs a diode to prevent the backfeed to the trunk light. When the stereo is on, it hits a frequency that sets off the sensor