Coil Splitting Vs Coil Tapping....
These are two terms we often hear when discussing pickups and switching options on electric guitars. More commonly we hear the term "coil tapping", but it seems that most people use them interchangeably. What is coil splitting vs coil tapping and how do we use them?
Let's start with coil splitting, because even though it is commonly mislabeled as "coil tapping", it is more often what we actually mean. Coil splitting is used on humbucking pickups to basically turn off one of the coils so that it acts as a single coil. This gives the player some flexibility in tone and output. Most humbuckers will lose about half of their volume (remember, half the pickup is shut off). Some pickups such as the
Centerpunch by
Dylanpickups.com is engineered to not lose volume when split.
How to Coil Split a Humbucker
If your humbucker has four wires coming out of it, it is relatively easy to do.
Find what is called either the "center link" wires of the pickup or the "finish" wires of each coil (refer to the manufacturer for color codes). In the illustration to the right, they are the green and black wires. Attach these wires to a switch and attach the other side of the switch to ground... That's it. You can use a separate switch, a push-pull pot, or a button to accomplish this. You can tie the center links of both pickups to one switch, or switch them separately depending on your preference and wiring setup.
Now you will have the flexibility of both single coils and humbuckers. A quick note..... If you have only two wires coming from each pickup, it's best to replace the pickups with 4-wire pickups to complete this project.
What is Coil Tapping?
Coil tapping as actually a process in the making of the pickup where the winder stops part way through the winding and adds an additional hook-up wire. It is typically used in high output single coils. The result is a three wire single coil that gives you the option of "full power" or the lesser output that was determined when the pickup was wound. This is a feature that needs to be designed into the pickup when it is built.
Lowering the output of the pickup at the flip of a switch gives you not only flexibility in output, but also tone. Usually, the lower output is also brighter.
Knowing the difference between coil splitting vs coil tapping may seem like splitting hairs more than pickups, but having the options is a lot of fun and the tonal possibilities are very cool.
http://youtu.be/hy_yIUAaLpQ
Find what is called either the "center link" wires of the pickup or the "finish" wires of each coil (refer to the manufacturer for color codes). In the illustration to the right, they are the green and black wires. Attach these wires to a switch and attach the other side of the switch to ground... That's it. You can use a separate switch, a push-pull pot, or a button to accomplish this. You can tie the center links of both pickups to one switch, or switch them separately depending on your preference and wiring setup. 
Now you will have the flexibility of both single coils and humbuckers. A quick note..... If you have only two wires coming from each pickup, it's best to replace the pickups with 4-wire pickups to complete this project.