Headlight switch is grounding 12v to body

You are WAY better of to actually learn what you are measuring with a conventional multimeter. Somebody is missing something here, I know not what. In this case even a simple test lamp might be better to find the problem

"Voltage" is always in reference to "something else." You can NOT have "voltage on the body" unless the battery is ungrounded, and even then, it will be in reference to the battery NEG post, or the POS post whatever.

For all I know, you don't have a ground wire from the block or the battery to the body