Ac Stuck On Defrost

if youre looking at the engine look to the right back (side with the battery) there will be lines running along the back and theyll all run to the same thing its a black box. look at it and there should be a really small line in the middle and on the black box it will say A/C inspect the line for any cracks or if its even put together. have the same problem with my 95 3.8 but i cant find the part anywhere. it has duck tape around it and it works fine.i know its a mickey mouse job but its good until i find the part