Well we tried, and no matter what we did we couldn't get a power reading on a single wire
The multimeter works, as we tried measuring the voltage of a battery, and that worked perfectly. We even took the wire out of the leads to try to get a better connection, but that didn't work. We think that we might not be finding a proper ground. We were using the metal radio bracket (also scuffed some of the coating off), so maybe that'* isolated from ground. We couldn't really see any other metal surface or screw that seemed to be grounded.
I think we'll either look for a test light or just find some car place that will hopefully be able to measure it better than we can.