ShuPIMPsky,

Since I don't have the wiring schematic for your equipment its hard to get into specifics.

FYI, negative, (-), and ground are all basically the same in this instance. It is the negative post of the battery. Your entire car frame is basically connected to the negative post of the battery. So any bare metal point on the car is a ground point.

That's great that you have access to a EE. I would have him look over the wiring diagram for the equipment.

Good luck!

-David