[Circ]

Sounds like it's somehow connected wrong. Mine goes up and down with the speakers and if I want more or less of it I just adjust the Bass slider in the EQ settings. A couple of clicks either way makes a noticeable difference in the subs volume. Anything below the midline on the Bass slider basically takes the sub out.

Since the wiring is pre-done with a pigtail, it's possible that the wires were put together wrong at Rockford. I'd check the wire colors and give Rockford Fosgate a call for a schematic to check it against. I had to call them about some missing parts and received great service from the guy who answered the phone.