Over the years I have seen several wiring fires under dashboards due to an insulator becoming conductive. As you can see in Photo 1 (left above) traces of Zinc from the stamped nut have been left on the insulating cardboard. If this zinc gets smeared or migrates to the edge of the cardboard a direct short to ground will result and cause a very smokey, burned mess under the dash. If the power is not turned off (even the battery unhooked) the entire wire harness can burn. Photo 2 (above right) shows a very simple solution. Every time I work on an instrument cluster I remove the nuts and place a piece of electrical tape over the stud and then replace the nut. It is a very simple and safe fix. I always do both terminals even though only one is shown above.