In this guide I will try to explain the best I can how the wiring of Single Coil Pickups (Strat, Tele, P-90 etc.) and how they relate to the overall wiring in your guitar. Normally single coils are run parallel to each other when using two pickups (ie. 2 and 4 position of a strat, mid position of a tele). It is possible to run them in series with one another to create a hotter and in some instances a true humbucking pickup!
Differences between Modern wound single coils and Classic wound single coils
Somewhere in the mid 80's Fender decided to begin implementing installation of a reverse wound/reverse phase middle strat pickup and tele neck pickup. And soon after other manufacturers followed. What this did was make the mid position on a tele and the 2 and 4 positions on a strat humbucking. This worked great and made those positions hum canceling, but it also got rid of the quack that was inherent in those positions.
Now lets look at what a humbucker pickup is. Its basically 2 single coil pickups, one of witch is reverse wound/ reverse phase wired together. This would be the same as the 2 and 4 position on a strat.
The difference is in a strat they are wired in parallel. The humbucker is wired in series. You will never get that fat heavy humbucker sound in a strat or in a tele for that matter without wiring the two pickups in series. There are a variety of ways to do this, push/pulls adding toggle switches etc.