I'm replacing the brake light bulb(whole socket actually) with one of these Products - elef. To install it I need to cut the original wires and solder the new bulb in place.
There's 3 wires for the stock bulb(brake, signal, ground I assume). There's 2 black and 1 yellow. I'm not sure which of the two black wires on the stock wiring is ground and which is for brake. I'm nearly positive that the yellow wire is for the turn signal. Anyone know which black wire is which? Or a way to test?

 

Bump

 

use a test light to find which one is a hot and which is a ground

 

That's what I'm gonna do I think. What's the process for that?

 

hook the end of it to a ground and if u touch the wire and it lights up it is a hot if it doesnt light up its a ground

 

easy enough. thanks.