Car Stereos: Left front cuts out, channel amplifier, rest work

Question
Having a problem with my left front channel cutting out in my car stereo.  I'm using kenwood KDC-X679 deck and KAC-8404 4 channel amplifier.  The problem is when I start my car and deck comes on the left front channel is off completly all the rest work fine.  Weird thing though is if I crank the volume it cuts back in. I have faded and ballanced to the left front only several times and the speaker will cut back in when I max volume.  If you have any ideas or troubleshooting steps that can help me out I would appreciate it.

Answer
Adam, It sounds like a classic short in the drivers side door jam.  That door is the most used, and the wires going into the driver's door get moved back and forth every time the door is used.  If there is a slight break in the wire, it will act exactly like you are describing.  I would not let it go too long.  If the wire wears a hole in the shielding, it will short on the door metal and possibly blow the amplifier.  Hope this helps, Scott