blairallday:
Thanks for the response Robin2!That's what I initially thought as well, but I think the red and black lines are meant to not be interfered with. Every time I connect to the black line it shorts the circuit.
I wish I could help you out with a datasheet, but it's a custom PCB. I'll get back to you if I can get.
Can you take a high resolution, well focused picture of both sides of the circuit board, as well as the connectors? Your description is confusing to me, and a visual reference might help. Sounds as if it may be malfunctioning. Connecting a ground to the ground wire should not disable the device.