Installed a JB and a 59 in an epiphone les paul special ii. Let me say that if the control compartment in that thing was any smaller I would have needed a microscope to find it. Anyhow, the 59 works great. Sounds awesome. The JB worked for 20 minutes until I shifted the wiring a little bit to wrap a short circuit in electrical tape, and now the sound is either extremely weak or nonexistent until I touch something metal like the pickup cover or the selector switch. It seemed like a ground issue but I reconnected the ground from the pickup and it still won't work. I don't own a multimeter and I'm running out of ideas here. I emailed Seymour Duncan customer support with my problem but I don't expect a reply from them until Monday, which is when I need this guitar for a concert. Worst case I'll break out the old stratocaster but it might not sound as good for what I'm doing.
You may have an open ground connection. Carefully retrace all your wiring and make sure it is correct and that your solder joints are good. That's about all I can tell you now, other than you should invest in a decent mutimeter. 20 bucks at Walmart.