Now that I see the pictures, looks like someone removed your heater assembly and installed some auxiliary AC unit that blows air from under the bonnet in the engine bay, through an AC evaporator to chill it (gas fumes, exhaust fumes, dust, leaves, and all).
To do this right you would be better off replacing what you have with something different.
Easiest would be a stock heater with a later under dash unit.
Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)