How You know you have negative or positive pressure.
I can say I know I have negative pressure. I unplugged one fan while the rest were spinning, and it slowed down then reversed direction as the air came down through it and was being pulled out by the other fans.
More aboutnegative positive pressure
Just for future advice, dont move/remove any connections while the power is on. As for the pressure the easiest way to know is just to count intake v exhaust. More intake, more positive and so on.