[green72s]

Thanks SunSoaked, that's a good point you're making. The cargo light is metal and the dome light is plastic. I originally thought the cargo light was supposed to ground through the housing, but now I'm thinking that it is not supposed to. For my most recent tests I have both the housings dangling so that they're not touching any metal.
When I button everything back up, I'll make sure neither are grounding.

There is a new update to the story. I checked the voltage at the fusebox and it's 6.9 to 7.0 volts. That seems like a problem. I'll post a picture of the terminal I'm connecting to that gives me that reading.