Submitted by 7StringedBeast - if you have any questions contact him. Ok I had to do this a couple months ago when I disassembled a guitar and forgot to write down the wiring diagram . It's pretty simple to do and useful for situations in which you don't know the color code for a pickup. I have written this in the simplest way possible, so that close to 0 knowledge in electronics is needed. All you need to know is how to operate a voltmeter. I won't get in details cause the purpose of this thread is to be a simple do-it-yourself thing. You will need: - Voltmeter/Multimeter - Metal screwdriver - Alligator clips (optional but makes the job much easier) - Pencil and paper - A pickup to test First draw a scheme of the pickup, just like it would be in the guitar. Draw two coils (in case it's a humbucker; if you got a single coil to test it's the same thing but with only one coil of course) and bridge/neck orientation. You don't want to memorize the colors so that when you are done you think "hmm what was it again?" and proceed to re-test the pickup. Something like this: Let's say I got humbucker X, and it's got a bare ground wire, and green, black, brown and blue wires (if you got a humbucker that's got only 2 wires and the ground wire it's easier, all you have to do is find out which wire is + and which is - just like a single coil). Set the voltmeter to read VDC (Volts Direct Current). Connect the voltmeter with the alligator clips to two of the wires (not the bare ground wire duh! ). I will try blue and brown to begin. Now to test the coils, tap the screwdriver all along the magnets on the top of one coil, and repeat for the other coil. Keep an eye on the voltmeter as you tap and pull the screwdriver off. The blue and brown wires did not show any reading for either of the coils. So, those wires do not go together. I try the black and brown wires next. When I tap the coil that is closest to the bridge I get a positive reading, and when I pull the screwdriver off I get a negative reading. This means that the black and brown wires are in phase for the "bridge coil". I proceed to make a note on my drawing: black is + (cause the negative alligator clip was attached to it) and brown is - (cause the positive clip was attached to it). So, now it is obvious that the blue and green wires are the ones for the other coil, but what is the correct phase? Attach the alligator clips to the blue and green wires, and tap the "neck coil" of the humbucker. I get a negative reading when I tap it, and a positive reading when I pull off the screwdriver. This means that the coil is hooked out of phase (the negative alligator clip is actually attached to the negative wire, green in this case, and the positive clip attached to the blue + wire, thus showing an out of phase reading). Write it down: blue +, green -. This step shows exactly what you are going to do for 2 wire humbuckers or single coils. Sweet! Now I can hook it to a switch and/or go crazy with series/parallel combinations.