J Pickup with 3 wires

[crackerjazz]

Hi guys, it's my first time to post here...hope you can help me I bought an old Fender Jazz bass. I wanted to re-wire
it because some wires have gotten loose, and got lost in
the process. I've tried rewiring it one way until I got the
tone I wanted, but then got this overpowering hum as
a result. I've tried other ways to rewire it to no avail.

I've searched for schematics on the web but
couldn't find any showing how to solder 3-wire J pickups.
All of the schematics I've seen have only two per pickup.
Is this some kind of split-coil pickup? I hope someone
has a schematic somewhere. Thanks in advance.

Those orange wires on the pots are mine. But those
wires from the pickups are the original ones.

http://farm5.static.flickr.com/4041/...f05264cd_o.jpg

http://farm5.static.flickr.com/4026/...c198a3c8_o.jpg

http://farm3.static.flickr.com/2781/...15273f1d_b.jpg

[line6man]

Did you take off the cover to see where the wires lead to?

The third wire is most likely a ground.

[metalmariachi]

I could possibly be a coil tap
Check with a meter between black and the other two.
If it is coil tapped, one will read around double the resistance of the other.

The black should go to ground.

Carefully popping the pickup out of the cover will help figure things out, It will be obvious if it is a split coil.

MM

[PunkRockDunn]

Active pup?

[GlennW]

I'm pretty sure that isn't a Fender pickup.

As far as the mystery wire, I'd guess it goes to a copper shield around the coil, but that's just a guess. I'd get a DMM or something that measures K ohms and try the probes on two wires at a time. I'd expect that one won't give a reading no matter which other wire the probe is on.

[4Mal]

I would also lose all those extraneous orange wires... all the split coil J pickups I've seen have had 4 wires. My guess is chassis ground.