OK...I've done this before no problem but this time is weird. Background is I bought this pre-wired V-V-T harness from bestbassgear and installed it in my Squier PJ bass a while back. I wired it with my existing pickups per the following document they provided and it worked great. On both pickups hot goes to the middle lug and ground goes to the first lug. So today I swapped pickups with Dimarzio Area J P-bass pickup and a Bartolini 9J SB1 and wired them identical to the diagram again, just like I had the other set of pickups and this is what happens. OK, I start with all 3 pots off. Then I turn the P volume pot up and no sound. I turn the P volume pot off and try turning just the J volume pot up and no sound. So I turn the Tone pot up and try both the P and J volume pots again and I have sound. So all I have to do to get sound out of both V pots is to turn the Tone pot up just a little bit even. It's almost like it's the volume pot but I also get more tone as I turn it up. I've included both the Dimarzio and Bartolini wiring diagrams (disregard the Bartolini example with the blend pot) and they jive with the diagram I used, so what could be happening? I've triple checked my installation and it's identical to the diagram.
Glad you got it fixed. How's the Apollo working out for you? It was my favorite jazz pickup for pairing with a P.
I already had an Apollo neck so I literally just got done installing them in my Squire CV 70's Jazz bass along with a new Babicz bridge. Haven't got done fully setting it up yet but initially it sounds way better than stock!
So what was the cause in your case? This happened to me a few years ago, because one leg of my tone capacitor was touching the pot casing. Bending that leg away from the pot fixed the problem.
The Area P's have a total of 6 wires between them. A red, black, white, green and two grays. When I got them they had been used before and the previous owner had the black and white spliced together and taped, and he had the two grays spliced together so I hooked up the hot and ground to the pots and left those other wires as is (I couldn't find a wiring diagram online). Well I finally found a wiring diagram for the Area J's and the two gray wires were supposed to be grounded also so I had just made an incorrect assumption. Problem solved!