Black box, filter? on DVD unit power/ign

I recently installed a DVD player in a customers vehicle and there is a sealed black box that has the 12v/gnd/ign going through it.  The customer brought the truck back saying that the dvd system won't turn on.  I troubleshooted it down to that box.  The ign won't pass through it.  On one side of the box I'll get 12v, and at the same time on the other side of the box I'll only get a ground. 

Is this box some kind of power filter, or what is it?  Should I just bypass the box for now until we can get another harness?

Thanks in advance.