Audi Repair: Audi A6, smooth transition, interior light

Question
Ok so I finally figured it out. I was going to change the load reduction relay and i noticed some black stuff on the 75x post  so I pulled the cables off and clean that terminal up and everything works fine. Now my main concern is it looks like the black was melting plastic there is also white powder in that area. Do you have any idea why this may have happened. And also my interior lights still act weird they go from bright to dim back and forth (not a smooth transition)

Answer
A bad contact can cause arcing which can really heat stuff up.  The plastic can be from the holder or from the support, keep things clean and check the current draw.  The interior light problem does indicate something is charging/discharging or arcing still.  Can you hear anything when this happens?  Normally there will be a buzzing from somewhere.  Let me know,  Jan