I’m gonna hard wire my radar detector in because I cant stand having messy wires and the cig lighter adapter hanging all over. Theres 2 wires I’m hiding out of site. One is all black and one is black with a white stripe. Need to know which is power and which is ground so I don’t screw anything up.

 

1) go to any store that sells electronics or car parts

2) buy a cheap multimeter

3) measure + and -

 

More often than not, the solid black wire is ground. But like Stocker suggested, it doesn't hurt to test the wires first.