Which wire is hot guitar pickup?
Each pickup has 2 lead wires. The Black Wire will be used as the Ground (note, on P90 Models, the Ground will be the Bare Inner Wire inside the Black). The other wire (Red, Yellow, or White depending on the model) will be the Hot Wire. Middle Position Pickups will have a Yellow Hot Wire.
How do you tell the polarity of a humbucker?
Simply place your compass on the pickup (Photo 2). The pickup's magnetic pole pieces will attract the opposite magnetic polarity end of the compass needle, which means the end that's pointing up away from the pickup indicates its polarity.