Help: Sterling JP60 with bridge pickup "weak" and strange wiring

Hi,
I’ve bought a Sterling JP60 (the “old” model in black with chrome hardware).
I bought the guitar used, it’s almost new, the last owner didn’t used it much but I have a problem: the bridge pickup sounds “thin”, without basses, low output and glassy. The neck pickup is good and I like it. When I opened the electronic I saw that the wiring was changed, even if the last owner said to me that he didn’t touch anything I saw that the white+black had heat shrink rubber to keep them “safe” but the black+red wires had insulating taper attached badly.

I cannot find online the original wiring but here’s the way all was connected:

– neck blue was on switch
– neck black+white together soldered
– neck red+bare on ground

– bridge blue was on switch
– bridge red+black together soldered
– bridge white+bare on ground

The only thing I could see online (I’ve found an image from a user) is that the bridge wiring had red on switch. I think that black+white together and blue+bare on ground but if I connect this way the pickup is silent.

I dismounted it and all connections seems ok, similar to neck one.
I’ve tryied to split the pickups with a push/pull pot and the neck splits perfectly (black+white) but the bridge don’t split (red+black or white+black). I don’t know if the pickup is faulty or some tech had modified the connections (I see the tape that insulates the coils a little torn near the wires, like someone modified it)

Can you help me? What should I try to know why this pickup has no bass at all? Both coils works but it seems like they are only trebly like almost a single coil. Anyone has the original wiring of the JP 60? I’ve asked to MM/Sterling but no response.

Sorry for mistakes, I’m Italian.

Regards 🙂