So, I'm having issues with the duct work in my 85 chev half ton. When I change the settings on my duct controls (defrost to vent, vent to floor etc.), nothing happens. It has something to do with the vacuum hoses attached to the air distributor (heater core box). I haven't a clue as to where these hoses feed off of or anything. Any information regarding the duct work and the vacuum hoses are much appreciated, thanks. NOTE: I'm not talking about the vacuum hoses on the engine, these are in the cab, just to clarify.