1986 GMC Jimmy Heater Defrost vent

I recently replaced the heater core in my 86 Jiimmy, everything works great! The heat is nice and hot and the fan blows great. But I noticed that when you turn the defrost switch on, the fan still blows nice and hard but it seems the door that opens and closes in the heater module isn't opening? And the air just kinda gets blown everywhere and not out the defrost vents where it should. I'm wondering if I hooked those hoses up wrong?(The hoses that are connected to the heater switch) Or does the air valve on the end of the heater module need to be replaced? I would like to get expert advice before I fool with this again cause it's such a pain pulling that module out, it's also 6.2 Diesel and it has that extra sound deadener in the engine bay, so the either the A/C has to be disconnected or the wheel well needs to come down. I'm not looking forward to it.