starting problems help

ok i bought a used IAC for my tracker and put it on the car. It still doesnt work correctly.
I have the tracker running kinda sorta...ok this is what I have done. I put the original IAC back on the vehicle .........I put the other new IAC on the firewall strapped down.. I unplugged the original IAC and plugged in the new one it is not connected to anything just plugged in......vehicle starts...why i have no idea.... there are hoses that connect to the IAC....two of them have coolant in them..........it seems as if the IAC has to be cool to work........i really need help if you have any ideas it would be appreciated...........thanks