I drive a 2000 Honda Civic and have two 12" Sony Xplod subs hooked up to a 1000W Sony Xplod amplifier. My problem started last summer. When my car is parked and the lights are off, the subs work perfectly. When i start driving they will cut in and out, usually working best when I am driving slow. The longer I drive, the better they seem to work. However, if my headlights are on they do not work at all, even if I am parked. Any ideas?

 

Give us some more info.
Check battery voltage with car working and when not working.
when driving and or when you turn on the head light is the amp going into protect if it has that feature or the amp have no power at all?
What you have for power wires for the amp?

Also check for loose connection and make sure you have a good ground location sanded to bare metal.