1993 Ford Explorer 4 by 4 button on dash board

4 by 4 button on dash board does not light up or engage 4 wheel drive when pushed.I checked all fuses and they where good.I was told to replace the shift motor on transfer case but I dont want to start buying parts because someone says to, and plus I dont know if it will fix it after I buy it.I purchased a manual and it doesnt say anything about the 4 by 4 switch or anything in trouble shooting. Is there a way I can test things to try to emlimanate buying a bunch of parts that are not broke. Thank you very much