My subs would never work when i turned the car on but they would start to come on after about 20 minutes of driving. I figured it was just the battery because its about 3 years old so i replaced it resterday with a sears die hard and it still has the same problem. Also, when the subs work and the battery is on or the car is running and the stero is off, every time a door is closed or i go over a bump in the road the subs hit kind of like its matching the sound the closeing or the bump makes. What could be the problem.
If you have a voltmeter, measure the voltage at the amp's power and remote turn-on terminals. If you have 12V on both terminals and the amp isn't powering up, there's a problem inside the amp. It could be a bad solder joint, even an unsoldered connection.