It sounds like you have a single stage. The defroster switch will only have one position. The W/Bk will be spare. With 2 stage there would be R/W R/Bk and Br going to the rear window.
In this picture of the rear electrical console, you will only have the black relay #2 if it is single stage. If you have item #6 the rectangular relay then it is 2 stage.
I am going to check a few things to check the W/Gr wire.
