83 no a/c heater flap postions?

[Bigstevex4]

Ok put new fan blows great new core both hoses to hot to hang on. the control in dash is not working right. so put flaps in max heat I think? The one under ash tray heat or defrost. that's easy the other 2 one blocks core. to control heat the 3rd vents into cab? Been fine with temps in 20s. but below zero does it pull warm air from cabin some how? Or just ice cold air from outside.