Jazz pickup volume dropped

[MxfmMod1k]

I just replaced my precision pickup on my mustang to the sd spb-4 and left the jazz stock. When in the middle position, the volume drops drastically. Has this happened to anyone?

Sorry about the title, Idk why I put jazz.

 

[Slater]

The pickups are most likely out of phase. Swap the hot and ground connections on the new pickup and you should be good to go.