pickups in combination - polarity

a quick identification can be done on single coils, if you get their tops together.
If you feel they attract each other, they should have different pole orientation.
This could imply a RW-RP pickup.

Then take a look at the hookup wires. There should be a black and a white cable (in most cases).
If one pickup's wires are connected to the opposite "eyelets" than the other's, then one of them is reverse wound (RW).

Of course this applies only to pickups of the same brand/model for obvious reasons.


Otherwise... connect them on the guitar and hear what they sound like...

EDIT--> If they sound thin, try to reverse the wires on one of them.

 

Most of the time, you won't know whether you have a problem until you actually mount the pickups. You can usually fix the problem, easily. If it is a Fender style Strat single coil, simply reverse the connections of the offending pickup. (If the neck+middle is out of phase, but the middle+bridge is in phase, the neck is the offending pickup. If the neck+middle is in phase, but the middle+bridge is out of phase, the bridge is the offending pickup. If both the neck+middle and the middle+bridge are out, the offending pickup is the middle.)

If the pickup in question has a coil ground lead that also serves as a drain for a metal base and/or cover, that drain will have to be isolated before you reverse the hot and ground wires for the coil(s).

 

That is true re. phase but not re. hum cancellation. With humbuckers in general it's easy to flip the magnet or you can turn them around 180 degrees (e.g. install a bridge pu with the screws coil towards the neck) to get the right coils to cancel hum with other pu's, but with single coils you do need to get them with opposite magnetic polarity if you want them to cancel hum when working together. You can drop a line to the manufacturers and they will tell you the magnetic polarity of their pickups. Many s/c's are offered with the RW/RP option, but if you're mixing different brands you will find they are not consistent. Even within the same brand (notoriously Fender) you can get different polarities depending on the specific model.