What is this, and what is suppose to be connected to it? I know it has something to do with vacuum, but I have no idea what I'm suppose to connect to it. Anyone have a hvac vacuum diagram or know where I can find one? Also, what's that gray "T" thing that comes off the heater core, and where does it go? When I bought my jeep, none of this was connected and the a/c and heat weren't working, I just replaced the heater core assembly, and now I'm trying to figure out how to get the air working correctly. Right now, it just blows in defrost only, and from what I've read, It sounds like a vacuum issue. Can anyone help me figure out where all the vacuum lines are suppose to be connected to?