newbie, seeking help..

[jwjbama]

I recently purchased a fusion 12 inch amplified sub. Most of the time the thing sounds great, but every now and then I get no sound from the sub. I have replaced the RCA cables as well is the head unit, but the problem still exists. It doesn't happen often, and by changing souces on the head unit the sound comes back. The power light on the amp stays constant, so does this sound like a grounding issue? Currently, the ground is attach to the trunk with a self tapping screw

[pickup1]

Was it new or used?

[jwjbama]

Used. Bought it from a cop who works with a family member. It was six months old and came from his moms (no kidding) car. She moved to a suv, and pulled it from her civic.