I just bought a 2004 Kia Sedona this past July. Looks great, runs strong, the only thing is when I run the A/C there is a hum that goes through the cabin. A passenger said that they felt a vibration under their feet, just behind the driver. I looked under the van and found a box with hoses and wiring attached. My questions; What is it? Could that be the problem? and Is this a common issue?.... A prepost Thank You to any help.