i think your referring to the heater tap, sounds like you have some weird aftermarket thing.
pictures came from searching ae86 heater diagram on google, there is a section on the heater in the manual, just download all the manuals from here in the tech docs thread and have a search
also i could be wrong but i think just about every 86 sold here had air con, and the odd ones out did not have the ac/econ buttons on the heater controls. either somebody swapped the heater control panel or your car never had air con