Heater problems on an AC car

I've got a 67 Valiant that originally has AC. I removed it because I had to swap engines and haven't put the AC back on. I connected the heater hoses to the engine and the heater still isn't working.

The hose that goes into the left side of the heater core has some kind of AC widget it connects to right before going into the heater core. The heater hose is hot up to that widget and the hose going from the widget to the heater core is cold. Also the hose going from the right side of the heater core to the engine is cold. I'm assuming this piece from the AC system is blocking the water from getting to the heater core. Any idea what that piece is and what I should do to fix it other than just buy a new heater hose and bypass it?