Photo 1

In several recent installments of Mod Garage, we’ve explored projects that involve humbucking pickups with 4-conductor wiring. I’ve received many emails from readers who want to do some of these mods on guitars equipped with generic humbuckers, but when they try to determine which wire goes where in their pickups, they’re stumped. They can’t find a color-code chart online, and when they contact the guitar’s manufacturer asking about the wiring, they often don’t get an answer.

If your guitar sports brand-name pickups—like DiMarzio, Seymour Duncan, Fender, Gibson, or even one of the many boutique pickup makers—it’s easy to suss out the 4-conductor wiring of the particular humbucker in your instrument. Chances are good you’ll find a color-code chart on the company’s website, and if not, these pickup makers typically have good customer support that can provide this information.

But when a guitar is outfitted with generic, unbranded pickups, it can be almost impossible to get the color-coding scheme. That’s because these pickups aren’t made at the guitar factory, but instead are supplied in large numbers by a specialized third-party manufacturer. Rather than following any standard, these suppliers use their own color coding and simply provide the guitar maker with instructions for installing the pickups in an instrument. As long as you don’t want to change the factory wiring, all is good. But if you want to experiment with mods, you’ll be out of luck because you lack the pickup’s color-code scheme.

My rant. This is a huge nuisance. I can’t understand why every pickup manufacturer feels the need to reinvent the wheel and use their own color-code scheme instead of a standardized chart. Good grief, people! As long as this nonsense continues, there will be no peace on Earth.

Pickup makers, if you read this: Why don’t you all plan a nice relaxing weekend somewhere (perhaps on a beach with umbrella drinks) with the goal of resolving this simple issue? It shouldn’t take more than 30 minutes to agree on a standard color chart for humbucker pickups. Your customers will be delighted and guitar techs worldwide will breathe a sigh of relief.

DIY cryptography. Fortunately, there is a way to solve the mystery of a generic humbucker’s color-coded wiring.Sure, if you have a fully equipped workbench with a digital scope, a pickup analyzer, and some other high-tech toys, it’s easy to crack the code—assuming you know how to operate these gadgets. But if you lack such high-end gear, I doubt you’ll be inclined to spend big bucks on it just to determine a humbucker’s internal wiring scheme.

So the question is, what’s the easiest way to crack the code without breaking the bank? All you need is the cheapest digital multi-meter (DMM) you can find, a screwdriver, and a standard compass or a pickup magnet polarity tester (such as the very affordable Schatten device that’s available from Stewart-MacDonald and other luthier-supply outfits). These items are a good investment for anyone wanting to mod guitar circuits.

Here’s the step-by-step procedure for determining the color code of a generic 4-conductor humbucker.

Photo 2

Step 1: Initial Prep

It’s much easier to work with a 4-conductor pickup if you first prepare its wires. After stripping the outer jacket covering the humbucker’s wires, you’ll find four thin, insulated wires, often twisted with each other, plus a fifth bare wire that we can ignore for this process. Why? Because that bare wire always goes to ground. No exceptions.

Now separate the four insulated wires. To do this, you’ll sometimes have to remove a thin plastic film that’s around them—we don’t need this now. Next, strip all four wires and twist their individual strands together. I like to pre-tin all four wires with a little solder, so the fine strands can’t untwist again (Photo 1). This makes the following tasks much easier.

Step 2: Pairing the Wires

Switch on your DMM and set it to “resistance”—the 20k ohms setting is perfect for this. If you have a fancy DMM with an “auto range” function, you can simply set it to resistance, which is usually marked with a Greek omega symbol (Ω) and your device will do the rest. Alternatively, you can set your DMM to “continuity” for this step, if your DMM offers this function. Instead of a reading on your DMM, you’ll receive an audio signal.

Next choose one of the four wires and touch it with the red probe of your DMM. Now touch every other remaining wire with the black probe. Only one of these three wires will give a reading on your DMM, showing the resistance of one coil, as in Photo 2. (If you set your DMM to continuity, you’ll get a beep instead of a LCD reading.) The two wires that give a reading belong to the same coil. Mark them or make a drawing, whatever you prefer. The two wires that are left will also give a reading and belong to the other coil of your humbucker. Verify this by repeating the same procedure with these two wires.

Tip: Here’s how to make the measuring a bit easier. Instead of using the DMM’s two probes, you can connect standard 4 mm banana-plug cables to your DMM. Attach an alligator clip, preferably insulated, to one end of each cable, and plug the other ends into the DMM. The cables and alligator clips are inexpensive, and they’re handy for all kinds of measurements.

Congrats—you’ve divided the four wires into two pairs, each belonging to one humbucker coil. This is an important step in our project. As far as our test humbucker, Photo 2 reveals the green and red wires belong to one coil, and the blue and yellow wires (shown) connect to the other coil.