This weekend I installed a 10” subwoofer in the inside of the rear ¼ panel, powered by an amp. Nothing special about the amp or the sub, I went the cheap route. The only other two speakers that are hooked up are the fronts powered by the head unit (pioneer). Last night everything sounded great, the next step was to hook up the rears to the other channel on the amp. However this morning, driving to work, I turned on the stereo to here some tunes and I get nothing but the bass from the sub. Checked the fade, not it. Got to work, opened the door too get out and guess what, speakers came on, closed the door, speakers off. I like it when my dome lights do that but this is ridiculous. Any suggestions?