How to figure out which side to install a pickup from out of a set
There are two ways to do this. One way doesn't work all the time and the other one does.
For a while now (possibly years at this point) I've had a pair of Fender Jazzmaster JM66 Japan model pickups in my possession, and they will probably be going into the 2017 Squier Vintage Modified Jazzmaster I recently acquired. These are pickups I received for free from a friend.
What I didn't know - and neither did the friend who gave these to me - is what position each pickup was supposed to be mounted in. The pickups have absolutely no markings on them whatsoever indicating where in the body they should be placed. Which is the bridge-side pickup and which is the neck-side? I had no idea, so I had to find out.
There are two ways to determine where in the body a pickup is supposed to be placed.
Method 1: Pole spacing
Guitar necks increase in width from nut to heel, and in many guitars the neck-side pickup has narrower pole spacing compared to the bridge-side.
However, there are a few issues with determining a pickup's body position this way.
First, some manufacturers don't even bother using front pickups with narrower spacing compared to the rear.
Second, this only works for pickups that have pole pieces you can see and moreover measure with a vernier caliper.
Method 2: Measuring ohm resistance with a multimeter
This is the easier and more accurate way to determine where a pickup should be placed in the guitar body. There is also an added bonus to doing it the multimeter way. At the same time you're checking the resistance, you're also checking if the pickup is dead or not.
The video below shows this in detail, but this is the process.
Pug in the red lead to the port on your multimeter where ohms can be measured. The black lead goes into COM as usual.
St the multimeter to measure ohms up to 20K.
Touch one multimeter lead to one wire of the pickup and the other multimeter lead to the other wire of the pickup, then read the multimeter display.
Write down what the reading was for each pickup. The pickup that had the highest reading is the bridge-side, and the pickup with the lowest reading is the neck-side. If testing pickups for a 3-pickup guitar like the Fender Stratocaster, the middle pickup would have a reading in between the bridge-side and neck-side values.
Confused? Watch the video below.
Is this always accurate for every pickup set?
For the vast majority of pickups, yes it is.
Most pickup sets, whether Strat pickup sets, Jaguar pickup sets, Jazzmaster pickup sets, P90 pickup sets or humbucker pickup sets have pickups where the bridge-side has the highest K value and the neck has the lowest value.
I personally do not know of any pickup set sold today that doesn't follow that formula. Some sets have a bridge-side pickup with a ridiculously high K value, but I don't know of any where the neck-side has a higher K than the bridge-side.
If you're wondering what would happen if you installed the bridge-side and neck-side in the wrong positions, the end result would be that one of your pickups would sound really weak, and when both pickups are selected, the sound would be pretty much useless. Nothing is damaged by installing pickups in the wrong position. It just sounds bad.
On a Stratocaster guitar, the middle pickup is the one that needs to be correct more than any other, because that's the one which is reverse-wound (unless it's a vintage period-correct set in which case it wouldn't be). It has to be in the right position or the guitar really won't sound good at all.
Why use 20K on the multimeter?
I do not know of any pickup that has a K value higher than 20K. I also do know know of any pickup that has a K value below 2K.
An average K value doesn't exist because pickup resistance values vary depending on how the manufacturer voices the pickup. However, generally speaking, you'll find most guitar pickups will have a K value of between 6 and 9.
And no, a higher K value doesn't translate to "better", because again, it depends how the manufacturer voices the pickup.
This is me showing and explaining how to get the resistance value.