92 explorer 4x4 not working

just bought the thing and the 4x4 dont work fuses are good, push switch to put it into gear works the electronic shift control module "black box drivers side behind that pannel" was broken i replaced it today but it still wont go into 4 wheel drive ...i dont have a book to tell me what fuse might go to it but they were all good ...should the light on the black box be light? when should it be light? should i try the moter on the transfer case? any thing i'm missing i'm new to this 4x4 stuff